Men reportedly wearing police uniforms opened fire in a dining area at the Mexico City international airport Monday, killing three federal policemen on an anti-drug operation as panicked witnesses sought cover. The killed agents had gone to the airport “to detain suspects linked to drug trafficking at Terminal 2," the federal Public Safety Department said in a statement, without specifying if the suspects also were police. “Upon seeing themselves surrounded by federal police, they [the suspects] opened fire on the officers." A witness said the shooters also were wearing police uniforms, and the Public Safety Department said it was investigating whether the shooters were active-duty police, former officers, or imposters. No suspects had been arrested following the shooting, which occurred at the food court at Terminal 2, near the area where vehicles drop off passengers but outside the internal security checkpoints where workers and passengers are screened.