Crash investigators late on March 22 said they do not yet know why a China Eastern jet carrying 132 people plunged from the sky, with recovery teams still scouring a forested mountainside for flight recorders from the pulverised Boeing aircraft.

No survivors had been found nearly 36 hours after the crash on March 21 – the deadliest air disaster in three decades in China, a country that had maintained an enviable air safety record.

“With the current information, we are unable to make a clear judgment on the cause of the accident,” Zhu Tao, director of the aviation safety office at China’s aviation authority, told reporters late on March 22.

He said the focus is now on “the search for flight recorders”.

Questions have mounted over the cause of the crash, which saw the stricken jet drop 6,100m in just over a minute before plunging into rugged terrain in southern China on the afternoon of March 21.

The velocity of the impact left twisted metal and passengers’ belongings scattered across a swathe of forest.

The airline has officially acknowledged that some aboard the jet, which was travelling from the city of Kunming to the southern hub of Guangzhou, had perished – but has stopped short of declaring all on board as dead.

Contact has been made with the families of all on board, said Sun Shiying, chairman of China Eastern Airlines Yunnan.

The crashed plane, which was nearly seven years old, had met all airworthiness requirements pre-flight, he told reporters at the press conference on March 22.

President Xi Jinping called for a full probe shortly after the crash as search teams armed with drones descended upon the site in a rural area of Guangxi province.

The Civil Aviation Administration of China has said it will conduct a two-week safety inspection across the industry.

On March 22, scorch marks were visible from the crash and resulting fire, rescue workers said, with one speculating that passengers had been “totally incinerated” from the intensity of the blaze.

A villager near the sprawling crash site, giving only his surname Ou, recounted hearing a “sound like thunder” followed by a blaze that blistered the surrounding hills.

A torn wallet and burned camera lens were among the eviscerated possessions captured on video by a reporter from the state-run People’s Daily who was able to enter the crash site.

But AFP journalists were blocked at a hillside checkpoint by a group of men identifying themselves as Communist Party members who said they had “orders from above” to prevent access.

The disaster occurred after a high-speed vertical nosedive, according to a video carried by Chinese media. AFP could not immediately verify the video’s authenticity.

Flight MU5735, which took off from Kunming shortly after 1pm (0500 GMT), lost contact over Wuzhou, a city in the Guangxi region, according to China’s aviation authority.

The foreign ministry said on March 22 they believed all passengers on board were Chinese nationals.

In Guangzhou airport, staff assisted loved ones of the 123 passengers and nine crew members aboard the plane, which stopped sending any flight information after dropping a total of 8,000m in altitude in just three minutes.

Relatives and friends of those onboard endured a grim wait for news.