MEXICO CITY – The helicopter crash that killed Mexican Interior Secretary Francisco Blake and seven other people in November 2011 was the result of pilot error, the government said.

The most likely cause of the crash was an “inappropriate decision” caused by near-zero visibility, the director of Airports and Auxiliary Services, Gilberto Lopez Meyer, said Friday.

Lopez said in presenting the final report on the crash at a press conference that experts ruled out the possibility of mechanical failure, a fire or an explosion.

The investigation showed the helicopter was traveling at a normal speed and had sufficient fuel, although thick fog severely impeded visibility and forced the chopper’s crew to alter their original flight plan.

The helicopter crashed into a mountainside on Nov. 11, 2011, while en route from the Mexican capital to nearby Cuernavaca. Killed along with Blake were four of his aides and the three-man air force crew of the Bell 407 aircraft.

U.S. and French experts assisted their Mexican counterparts in analyzing all aspects of the flight.

With a hand in everything from law enforcement to disaster relief and running elections, Mexico’s Interior Secretariat can be roughly described as a combination of the U.S. departments of Justice and Homeland Security.

The interior secretary is Mexico’s second-most-powerful official after the president.

The 45-year-old Blake was a key figure in President Felipe Calderon’s struggle with drug cartels and organized crime, a conflict that has claimed more than 60,000 lives over the past six years.

Blake’s death came three years after the Nov. 4, 2008, plane crash that killed then-Interior Secretary Juan Camilo Mouriño.