MOSCOW (Reuters) -- Russian prosecutors say they are to check safety standards at national carrier Aeroflot after a plane operated by one of its subsidiaries crashed, killing all 88 people on board.
A Boeing 737-500 operated by Aeroflot subsidiary Aeroflot-Nord crashed as it tried to land in the Ural Mountains city of Perm in the early hours of September 14, in Russia's worst air crash for two years.
A spokeswoman for Aeroflot said the checks by prosecutors were routine and the company was confident it was in compliance with safety regulations.
A statement from the Prosecutor-General's Office said investigators had been instructed to "conduct checks on the implementation of aviation and flight safety laws in Aeroflot-Russian Airlines and its subsidiaries."
It said the investigation was being launched in connection with the September 14 crash. Investigators initially blamed engine failure for the crash but they said today that was not their only line of inquiry.
Aeroflot spokeswoman Irina Dannenberg said the checks into the company's safety standards would start on September 17.
"Such checks occur regularly. The recent disaster has given the reason to conduct another one," she said. "We are in excellent condition and there has never been any difficulty."
Aleksandr Bastrykin, head of the Investigative Committee of the Prosecutor-General's Office, which is leading the crash investigation, said on September 14 a technical fault on the plane's right engine was the most likely cause of the crash.
"But that explanation is far from being the only one which is being painstakingly examined by investigators," Bastrykin's press service quoted him as saying in a statement.
He did not list the other possible causes. Russian state television said these could include a mistake by the crew, low quality fuel or a dangerous cargo in the aircraft's hold.
Russia's domestic intelligence agency has said explosives could not have brought down the aircraft. Some witnesses said they heard an explosion while the jet was still in the air, and debris was scattered over a large area.
"It will only be possible to draw final conclusions after the 'black boxes' have been processed and after the results are received from complicated forensic studies," the statement quoted Bastrykin as saying.
Russia's airline industry has improved its patchy safety record in the years since the collapse of the Soviet Union and the September 14 crash was the worst since 170 people died in August 2006 when a Russian TU-154 plane crashed in Ukraine.