Britain's Office of Fair Trading (OFT) said a joint operation with police had shut down websites run by Euroteam, an unauthorized ticket trader based in Oslo, Norway.
Euroteam had obtained some 5,000 real tickets for the games illegally. Some of those tickets were seized by police in Oslo this week, and appeared to have been supplied to Euroteam from eastern Europe, Norway's most senior Olympic official told The Associated Press.
"We think that they are coming from two countries in eastern Europe," said Gerhard Heiberg, a member of the International Olympic Committee. "This is not a good case. We hate that it has happened in Norway."
Heiberg said it was not clear if the seized tickets were sold to the black market by international sports officials.
London Games tickets are valid only when obtained through authorized outlets or are allotted to the so-called "Olympic family," which includes national Olympic committees, sports federations, sponsors and athletes.
The OFT, Britain's consumer protection service, said the investigation led Euroteam and its director Andreas Gyrre to make a deal at a court in London. It said Euroteam would "provide a full refund to any of their customers who either do not receive their tickets or are refused entry to an event," the government body said in a statement.
Gyrre did not immediately respond to a message from The AP requesting comment.
Euroteam wrote to customers this week explaining that "a lot" of their tickets had been confiscated as part of British efforts to stifle black market sales.
Heiberg said the IOC would "want to investigate what has happened and stop it."
The IOC is already reviewing evidence provided by The Sunday Times which alleged that dozens of Olympic officials across the world had offered to sell their allocated tickets to the newspaper's undercover reporters who were posing as black market agents.