Mexico's federal police agency has replaced all 348 officers at the capital's international airport after police there shot dead three of their fellow officers believed to be involved in drug trafficking.

The new agents have been drawn from across Mexico and have all passed double vetting and background
checks, Luis Cardenas, regional federal police chief, said on Sunday.

Three federal policemen have been charged in the June 25 Mexico City airport killings. One of those officers is in custody while two others are on the run.

Cardenas said the officers were involved in smuggling in cocaine from South America and attacked officers who spotted their wrongdoing.

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From their hiding place, the fugitive officers told Proceso magazine that they had no links to drug trafficking, and accused their superiors of trying to coerce them into getting involved in organised crime.

Luis Cardenas Palomino, federal police regional security chief, said his agents discovered that passengers arriving from Peru would hide drugs in a bathroom before going through customs.

Corrupt police would later retrieve the drugs and sneak them out of the airport.

All the other federal police officers who worked at the airport have been reassigned to other posts across Mexico,
Cardenas said.

There have been more than 55,000 drug related killings, including those of 3,000 police officers, in Mexico since President Felipe Calderon took office and launched a crackdown on drug cartels in late 2006.
 
Enrique Pena Nieto of the opposition Institutional Revolutionary Party will assume the presidency in December and
has promised to quickly reduce the number of drug-related killings.