A June 25 shootout at this capital's airport that left three police officers dead began with an argument among cops over a packet of cocaine, a leading Mexican newspaper said Friday.

The official account maintains that three Federal Police officers under investigation for drug trafficking killed three fellow officers who were about to arrest them at Benito Juarez International Airport.

Reforma, however, cites several unnamed witnesses who said the shooting arose from a dispute among six police officers over a packet of cocaine left behind by a traveler.

Sources in airport security had told Efe earlier that five or six cops, including several off-duty officers in plainclothes, were together at a coffee shop in the terminal shortly before the gunfight broke out.

The police arguing about the drugs went to the airport's food court, described as a "blind spot for the security cameras", where the shooting started.

Two officers, Josue Adan Matadamas Cota and Enrique de Jesus Pacheco - who was at the airport on his day off - died in the food court.

"Apparently, some uniformed officers tried to escape by elevator and were confronted by Fidel Rojas Martinez, who was wounded and later died," Reforma said.

At least 10 cops were involved in the shooting, the newspaper said, contradicting authorities' statement that only six officers took part.

The head of the Federal Police division of Regional Security, Luis Cardenas Palomino, called Reforma's story a "disgrace" and said authorities had no evidence or testimony pointing to "any argument" among the officers.

The three suspected dirty cops the government blames for the killings remain at large.

Authorities have presented security videos that appear to support the official account of the events of June 25. EFE