Mexico's Secretary of the Interior, Francisco Blake Mora, has died in a helicopter crash near Mexico City. The helicopter was flying to Cuernavaca in neighbouring Morelos state for a prosecutors' meeting when it went down. All eight people on board were killed. President Felipe Calderon said weather conditions were probably to blame. Mr Blake Mora, 45, was appointed to the post last year and was a key figure in the war against drug cartels. The helicopter had initially been reported missing. Some Mexican media reports said there was heavy cloud at the time. Peter Bowes says Mr Blake Mora was seen as a hardliner who battled Mexico's drug problems "Unfortunately the interior secretary, his [assistants] and the helicopter crew were found dead," government spokeswoman Alejandra Sota said. Deputy Interior Secretary Felipe Zamora Castro and the interior ministry's chief press officer Jose Alfredo Garcia Medina were also killed in the crash along with other government officials and the air force crew, Ms Sota said. She said a search for the helicopter began when it was discovered it had strayed from its planned course. Mexican television showed wreckage from the helicopter strewn across a hillside. Ms Sota said the craft went down in the Xochimilco area, just south of Mexico City. "The cloudy conditions at the time certainly make you think about the probability of an accident," President Calderon said in a televised address. He said a thorough investigation of the accident was being launched and cancelled a trip to Hawaii for the Asia-Pacific Economic Cooperation (Apec) forum. US President Barack Obama called Mr Calderon to offer his condolences, a US government spokesman said. Mr Obama "reinforced his commitment to the close partnership between the United States and Mexico in this difficult time," said US National Security Council spokesman Ben Rhodes. Drug war hardliner The interior secretary is Mexico's senior cabinet position and the top official after the president, with responsibility for domestic affairs and security. Mr Blake was Mr Calderon's fourth interior secretary. One of his predecessors, Juan Camilo Mourino, was killed in a plane crash in Mexico City three years ago. Mr Blake began his political career in the north-western border city of Tijuana in the mid-1990s, later serving as interior secretary for Baja California state. Map of Mexico He also served as a federal congressman from Mr Calderon's National Action Party. He earned a reputation as being a hardliner in Mexico's struggle with drug cartels. Mr Blake Mora frequently travelled to cities badly affected by the cartels, such as Veracruz and Ciudad Juarez, to help co-ordinate the government's response. More than 40,000 people are reported to have died from drug-related violence since President Calderon sent in the army to help combat the cartels in 2006.