MAYFLOWER, Ark. - Exxon Mobil Corp. says crews are working to contain and clean up an oil spill near Mayflower, Ark., after its Pegasus pipeline ruptured Friday afternoon.

The pipeline carries Canadian heavy crude oil from Patoka, Illinois to refineries on the Texas Gulf coast.

Exxon Mobil issued a release saying the company was responding to a spill of more than 10,000 barrels, and that some 4,500 barrels of oil and water had been recovered.

The latest spill comes at time when proponents of the proposed Keystone XL pipeline have been trying to convince Washington to give the $7 billion project the green light.

Opponents of TransCanada Corp.'s plan to pipe Alberta oilsands bitumen to the U.S. Gulf Coast denounce it as an environmental catastrophe in the making.

Dan Gatti of the advocacy group Environment America says the Arkansas spill provides a glimpse into what would happen if the Keystone pipeline got built.

"These images of oil-coated disasters need to become reminders of a bygone era, not a sign of things to come," Gatti said in a statement Sunday.

Exxon said the 20-inch pipeline had been shut down as crews tried to prevent the spilled oil from reaching a nearby lake.

It said cleanup operations were being co-ordinated with the Department of Emergency Management and other local authorities, and that the cause of the spill was being investigated.

Last Monday, federal regulators proposed that Exxon Mobil pay $1.7 million in civil penalties for safety violations linked to a pipeline rupture that spilled an estimated 238,000 litres of crude oil into Montana's scenic Yellowstone River in July 2011.

The spill fouled approximately 110 kilometres of the Yellowstone River's banks, killing fish and wildlife and prompting a massive, months-long cleanup.

Related on HuffPost:

Loading Slideshow...
  • 10. Walmart Stores

    Wal-Mart employs more than 2 million people, making it the largest company in America by head count. In the most recent Fortune 500 ranking, Wal-Mart fell just behind Exxon Mobil in total revenue. Wal-Mart is made up primarily of three divisions: Walmart’s domestic stores, its Sam’s Club warehouse operation and Walmart International. <strong>Forecast 2013 revenue:</strong> $467 billion, up 5% <strong>Forecast 2013 earnings: </strong>$16 billion, up 10% <strong>52-week range: </strong>$57.18 – $77.60 <strong>Market cap: </strong>$228.68 billion

  • 9. Pfizer

    Pfizer’s big challenge, like that of most other large pharmaceutical companies, is the expiration of patents for much of its drug portfolio. Cheaper, generic versions of these drugs have taken market share. In a recent example, Pfizer had to drop the price of Viagra in Canada to compete with generic versions sold there. Pfizer has gone through a series of layoffs to protect its margins, most recently at its U.S. sales operations. In the latest reported quarter, revenue fell to $14 billion from $16.6 billion in the same period a year ago. <strong>Forecast 2013 revenue:</strong> $58 billion, down 1% <strong>Forecast 2013 earnings:</strong> $17 billion, up 6% <strong>52-week range: </strong>$20.75 – $26.77 <strong>Market cap:</strong> $197.02 billion

  • 8. General Electric

    GE is considered the world’s largest conglomerate. It provides global infrastructure products and services, health-care systems, jet engines and transportation services, and household appliances. It also has a large financial services division. One of the major criticisms of GE management is that the company has grown very little over the past several years. Wall Street has reacted negatively, and the stock price has fallen by more than a third over the past five years. <strong>Forecast 2013 revenue: </strong>$148 billion, up 2% <strong>Forecast 2013 earnings: </strong>$18 billion, up 11% <strong>52-week range: </strong>$18.02 – $23.18 <strong>Market cap: </strong>$222.00 billion

  • 6. IBM (tie)

    IBM is one of America’s largest tech companies. It is also one of the most diverse. Its strength in sales to corporations and government has allowed it to largely avoid many of the troubles that have faced firms like Dell Inc. and Hewlett-Packard Co., which are more dependent on sales to consumers. IBM has significant operations in Europe and Asia. It sells hardware—including mainframe computers—software and IT services. It also has consulting operations and a finance division. IBM is one of America’s oldest tech companies, and in 2011 celebrated its 100th anniversary of its founding. <strong>Forecast 2013 revenue: </strong>$107 billion, up 2% <strong>Forecast 2013 earnings: </strong>$19 billion, up 10% <strong>52-week range: </strong>$177.35 – $211.79 <strong>Market cap: </strong>$217.94 billion

  • 6. Wells Fargo (tie)

    Wells Fargo & Co. is one of America’s “big four” commercial banks, alongside Chase, Citigroup Inc. and Bank of America Corp. The company recently reported better-than-expected earnings. An indication of Wall Street’s admiration for the bank is that its share price has well outperformed its peers over the past five years. Like the other large American banks, Wells Fargo is highly diversified. It has retail bank operations, commercial operations that handle business lending, an investment bank and a wealth management business. <strong>Forecast 2013 revenue: </strong>$85 billion, down 1% <strong>Forecast 2013 earnings:</strong> $19 billion, up 9% <strong>Range: </strong>$28.77 – $36.60 <strong>Market cap:</strong> $186.36 billion

  • 5. J.P. Morgan Chase & Co.

    J.P. Morgan Chase has had its share of trouble recently, including a large trade that cost the bank more than $6 billion. It was made by London investment employee Bruno Iksil, who has been called the “London Whale” because of the magnitude of the hit to J.P. Morgan’s financials. The company readily admitted that poor management was the cause of the problem, which cost the bank’s chief investment officer her job and caused execs to replace the head of London trading operations. <a href="">Read related story: Goldman, J.P. Morgan rise as results scrutinized.</a> <strong>Forecast 2013 revenue: </strong>$100 billion, up 2% <strong>Forecast 2013 earnings:</strong> $20 billion, up 6% <strong>Range: </strong>$30.83 – $46.49 <strong>Market cap:</strong> $175.44 billion

  • 3. Microsoft (tie)

    Microsoft, once the most powerful and largest software company in the world, has fallen on hard times. Global PC sales have slowed considerably. Unfortunately for Microsoft, PC sales aren't expected to improve this year, as consumers move to tablets and smartphones. Microsoft has several other challenges, as its Online Services Division has struggled with losses. Microsoft has also had trouble gaining adoption of its mobile Windows product, which relies in large part on its partnership with handset giant Nokia Corp. <a href="">See the full story at 24/7 Wall St.</a> <strong>Forecast 2013 revenue:</strong> $80 billion, up 9% <strong>Forecast 2013 earnings:</strong> $24 billion, up 7% <strong>Range:</strong> $26.26 – $32.95 <strong>Market cap:</strong> $222.70 billion

  • 3. Chevron (tie)

    Chevron is the third largest company in the U.S., based on revenue, according to Fortune, behind only Wal-Mart Stores and Exxon Mobil. Like most of the other large U.S. oil and diversified energy firms, much of Chevron’s revenue comes from overseas. In the most recent quarter, Chevron’s total sales were $55.7 billion, of which $32.4 billion was pegged as international. Chevron’s stock has outperformed those of most of its global peers over the past five years and has risen 20% over that period. <strong>Forecast 2013 revenue:</strong> $260 billion, up 8% <strong>Forecast 2013 earnings: </strong>Flat at $24 billion <strong>Range:</strong> $95.73 – $118.53 <strong>Market cap: </strong>$216.21 billion

  • 2. Exxon Mobile Corp.

    Exxon Mobil Corp. is the world’s fourth largest oil company, the largest company in the U.S. based on revenue, and the second largest public corporation in the world based on market capitalization. As with most of the world’s largest energy companies, Exxon has embraced the clean energy and fuel efficiency movements. The amount Exxon said it would spend to expand its business in the next five years is staggering. In its annual “Outlook for Energy,” the company said it expects to invest $185 billion in energy projects in the period. <strong>Forecast 2013 revenue: </strong>$473 billion, down 1% <strong>Forecast 2013 earnings: </strong>$37 billion, up 2% <strong>Range: </strong>$77.13 – $93.67 <strong>Market cap:</strong> $406.24 billion

  • 1. Apple

    Apple is arguably the most widely covered company by the press. More than a year after the death of co-founder and CEO Steve Jobs, Apple’s efforts to maintain its pre-eminence in the smartphone and tablet PC markets are under constant scrutiny. Apple’s pace of change has been remarkable. In 2007, when the iPhone was launched, the company was a PC and portable music player company. Now, the iPhone accounts for almost half of Apple’s revenue and two-thirds of its profits. Apple’s lead has been eroded by competition from a broad array of products from other companies, led by the Samsung line of smartphones and’s Kindle tablet. Apple’s strength in the app business, in which it has had a mammoth lead. <strong>Forecast 2013 revenue:</strong> $191 billion, up 23% <strong>Forecast 2013 earnings: </strong>$46 billion, up 10% <strong>Range:</strong> $418.66 – $705.07 <strong>Market cap: </strong>$491.60 billion