LONDON (AP) ― A black market operation in London Olympics tickets has been stopped and buyers of 20,000 seats will be denied entry to venues, the government said Wednesday.

Britain’s Office of Fair Trading 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.