Recovery crews on Sunday found the second black box — the flight data recorder — from the wreckage of a China Eastern Airlines Boeing 737-800 jet that crashed into a mountainside in southern China.

Flight MU5735 crashed on Monday, killing all 132 people onboard, mainland China’s deadliest aviation disaster in 28 years.

Heading to coastal Guangzhou from the southwestern city of Kunming, the plane dived from cruising altitude around the time it should have started its landing descent. The dead included nine crew members.

The black box, which could shed light on the cause of the crash, has been sent to Beijing for examination and analysis, state media reported. The other black box — the cockpit voice recorder — was delivered to experts in the Chinese capital after being found on Wednesday.

It was too soon to determine the cause of the crash, and crashes are usually the result of a combination of factors, experts said.

The second black box was dug out of a slope at the crash site about 9.20am in muddy conditions after rain in recent days.

The device, part of which was badly damaged, was recovered 1.5 metres (5 feet) underground and 40 metres (130 feet) from the point of impact, said Zhu Tao, head of aviation safety at the civil aviation administration of China.

“Civil aviation investigators at the site confirmed that the storage unit of the flight data recorder has been found,” Zhu told a news conference in Guangxi. “Parts of the recorder were seriously damaged, but the outside of the storage unit was in fairly good condition.”

The crash was the deadliest since a China Northwest Airlines flight from Xian to Guangzhou crashed, killing all 160 people on board.