(AP) - Federal drug enforcement agents showed up unannounced Sunday to check at least two visiting NFL teams’ medical staffs as part of an investigation into former players’ claims that teams mishandled prescription drugs.

There were no arrests, Drug Enforcement Administration spokesman Rusty Payne said Sunday. The San Francisco 49ers’ staff was checked at MetLife Stadium in East Rutherford, New Jersey, after they played the New York Giants. The Tampa Bay Buccaneers’ staff was checked at Baltimore-Washington International airport after playing the Redskins.

The operation was still ongoing, and other teams may be checked later Sunday, Payne said.