A helicopter crash that killed a Cabinet minister and his deputy appears to have been caused by bad weather, officials said Thursday, denying suggestions that the flight had been sabotaged.

While one official aboard the craft had received death threats from a drug trafficker, authorities said that poor visibility probably was to blame for Wednesday's crash that killed Public Safety Secretary Ramon Martin Huerta (search) and Federal Preventive Police Commissioner Tomas Valencia (search), in addition to five other passengers and two crewmembers.

Foreign Relations Secretary Luis Ernesto Derbez (search) said he has called foreign diplomats, including the U.S. ambassador, to assure them experts had determined the crash was an accident, despite the reported death threats over drugs.

"It is important to send an immediate message to the entire world, and to Mexico, so that it is quite clear to everybody that nobody is covering up anything and that what we have here is an unfortunate accident," Derbez said.

The helicopter went down shortly after taking off from Mexico City, striking a mountainside about 20 miles outside the capital and scattering debris among pine trees at the 11,200-foot crash site.

"All the elements that we have at hand, all the experts that were consulted, say that there is sufficient evidence to consider that we are dealing with an accident," presidential spokesman Ruben Aguilar said at a news conference. "But we must wait for the results of the investigation."

Civil aviation authorities at the Communications and Transportation Department were leading the investigation.

The first body recovered from the scene was airlifted Thursday morning to the offices of the Mexico State attorney general's office for identification.

"They all died in the line of duty," President Vicente Fox (search) said in a televised address Wednesday, his voice cracking with emotion. "They are heroes. ... I have lost not just a co-worker, but a close friend, Ramon."

Martin Huerta (search) led Fox's campaign for state governor in Guanajuato in 1995.

As public safety secretary, Martin Huerta was a key figure in Mexico's fight against drug gangs and he led a campaign to clamp down on security at high-security prisons. He had been headed to La Palma prison outside Mexico City for a swearing-in ceremony for new guards.

Also among the dead was Jose Antonio Bernal, an official from the country'sNational Human Rights Commission (search). It announced shortly after the helicopter disappeared that Bernal been threatened in the past by reputed drug lord Osiel Cardenas (search), reportedly for refusing greater privileges for Cardenas in prison.

Aguilar said officials were puzzled by the announcement, calling the timing of the commission's letter so soon after the crash "strange."

Martin Huerta was appointed to lead Public Safety in 2004 after the previous secretary, Alejandro Gertz Manero, resigned to return to private life.

Valencia had been promoted to his police chief post, answering to Martin Huerta, in January after his predecessor was fired for a botched response to an attack by a mob in Mexico City that left two federal agents dead.