Passengers were terrified when oxygen masks dropped from a plane as it plunged 23,000ft - leaving them fearing it would crash.

The Boeing 737 had departed from Shanghai Pudong Airport in China bound for Tokyo, Japan, when it suddenly began to descend on Monday, June 30.

Footage shows travellers using oxygen masks amid fears that the change in pressure levels would cause some people onboard to lose consciousness.

One passenger said: 'I heard a muffled boom, and the oxygen mask fell off in a few seconds. The stewardess cried and shouted to put on the oxygen mask, saying the plane had a malfunction.'

Another traveller added: 'Suddenly, all the oxygen masks popped open while I was sleeping.'

Local media reported that the flight JL8696/IJ004, was operating under a codeshare agreement between Japan Airlines and its low-cost subsidiary, Spring Japan.

The plane was carrying 137 passengers and six crew members when it experienced a mechanical issue during the flight, prompting a rapid descent from 32,800ft (10,000m) to 9,800ft (3,000m) within 10 minutes, at approximately 6:40 pm.

Authorities said that an alert indicating an abnormality in the aircraft's pressurisation system was triggered. The pilot then declared an emergency to air traffic control and diverted to Kansai Airport.

The aircraft made an emergency landing at Osaka Kansai International Airport at 7:50 pm. No injuries were reported.

An investigation has been launched to determine the exact cause of the incident.

Passengers said the airline later offered 15,000 yen (93 USD) in transportation compensation and provided one night of accommodation.