Mexican federal police on Thursday offered a reward of 5 million pesos ($370,000) to help capture two officers accused of drug trafficking and shooting dead three other policemen inside the capital's international airport.
The wanted officers had gone into the airport bathroom to receive cocaine from a Colombian traveler before the three policemen tried to arrest them on Monday, said Luis Cardenas, division head of the federal police.
The officers opened fire and fled the airport along with another policeman who is also on the run, Cardenas said, calling them "traitors." The shooting happened in front of food courts and panicked travelers threw themselves to the ground.
The incident is a major embarrassment for the government of President Felipe Calderon, who has put the federal police at the heart of a five-and-a-half-year-long offensive against drug gangs.
More than 55,000 people have been killed in drug-related violence in Mexico during that time.
On Sunday, Mexicans will vote for a new president to succeed Calderon, who is limited to one term in office.
Most opinion polls predict Enrique Pena Nieto, the candidate of the opposition Institutional Revolutionary Party or PRI, will win the election by a wide margin.