Air China pilots investigated after sudden 25,000-foot plunge

July 12 (UPI) -- Chinese authorities are investigating an Air China flight this week, on which passengers were startled by a sudden loss of altitude -- 25,000 feet in just a few minutes.

China Air Flight 106 was en route from Hong Kong to Dalian, China, Tuesday night when officials say it lost the altitude over a 10-minute span. The fall was severe enough the automated flight systems deployed oxygen masks in the passenger cabin.

State news agency People's Daily China reported the abrupt descent may have been caused by pilots smoking in the cockpit.

An in-flight announcement said decompression of the passenger cabin caused the emergency descent.

Flight 106, with 162 passengers and crew, landed safely in Dalian.

Air China said the Civil Aviation Administration of China is investigating. The carrier vowed "zero tolerance" if the crew is found negligent.