Mexico City - The pilot of the plane that crashed last week in Mexico City killing Interior Minister Juan Camilo Mourino and 13 others did not keep enough distance from another plane, which may have caused the crash.

Mexican Transport Minister Luis Tellez said Friday that there were indications that the resulting turbulence "may have been a factor that contributed to the fall of the plane," but the investigation is ongoing to prove what he now called a "solid hypothesis."

Mourino, former Mexican drug czar Jose Luis Santiago Vasconcelos and seven other people on board the plane were killed in the crash, along with five others on the ground.

The small Learjet 45 was preceded by a Boeing 767 operated by Mexicana de Aviacion that was coming in from Buenos Aires and was approaching Mexico City airport.

The preliminary investigation indicates that the Learjet 45 pilot took over one minute to reduce his speed and keep an appropriate distance from the other aircraft, after being required to do so by the control tower.

That caused turbulence that the pilot himself blamed on the nearby larger plane, according to communication registered in the flight recorder.

The required distance between planes amounted to 5 nautical miles, but "the last distance recorded on radar was 4.15 nautical miles," Tellez said. (dpa)