The action came after allegations during congressional hearings last week that at least one engineer tried to cover up the switch problem by fixing it without changing the part number.
GM, in a statement Thursday, said the engineers were placed on leave after a briefing from former U.S. Attorney Anton Valukas, whom GM has hired to figure out why it took the company more than a decade to recall the cars. GM says at least 13 people have been killed in crashes linked to the problem, but family members of those who died say the death toll is much higher.
Company spokesman Greg Martin would not identify the engineers.
"This is an interim step as we seek the truth about what happened," CEO Mary Barra said in the statement. "It was a difficult decision, but I believe it is best for GM."
GM is recalling 2.6 million compact cars worldwide, including the Chevrolet Cobalt and Saturn Ion, to replace the switches. The Justice Department and the National Highway Traffic Safety Administration are investigating GM's slow response to the problem.
During congressional hearings on the matter last week, Sen. Claire McCaskill accused one GM engineer of a coverup. Ray DeGiorgio, the lead switch engineer on the Cobalt, said in a deposition last year for a lawsuit against GM that he never approved a change to the ignition switch. But McCaskill produced a document from GM's switch supplier that showed DeGiorgio signed off on a replacement, but with the same part number. Failing to change a part number makes the part harder to track.
"What we don't know yet is how many people knew about the changing of the defective part and hiding that change behind using the same part number," McCaskill said after the hearing. "It may have been isolated to a small number of engineers that were trying to cover themselves. There was a culture of ... covering up the problem as opposed to being accountable for the mistakes they've made."
During the hearings, Barra called the failure to change the part number "unacceptable." She said at the time that the company has not fired any employees in connection with the recall. But she said if inappropriate decisions were made, GM will take action, including firing those involved.
GM would not make DeGiorgio available for an interview. He did not return telephone messages left by The Associated Press. A recording on DeGiorgio's work telephone number says he's away from the office and refers business calls to two other GM employees.
Also Thursday, GM announced a program to recognize employees who speak up when they see something that could affect the safety of customers. "GM employees should raise safety concerns quickly and forcefully, and be recognized for doing so," Barra said in the statement.
The company said she announced the program, called "Speak Up for Safety," at an employee meeting Thursday.
Employees also will be recognized for ideas that make vehicles safer, the statement said.
No details of the program were given, but the statement said they will be announced within the next 30 days.
The ignition switches on the small cars can unexpectedly slip out of the "run" position to "accessory" or "off." That shuts off the engine and the power-assisted steering and brakes and can cause drivers to lose control of their cars. It also disables the air bags. In many of the crashes, drivers have inexplicably veered off the road or into traffic.
Parts to begin fixing the cars are to start arriving at dealerships on Friday. But Barra has said it likely will take until October before all the cars are repaired.
Shares of GM rose 21 cents to $33.83 in morning trading Thursday.