KUALA LUMPUR, Malaysia (AP) — Malaysia Airlines said one of its flight en route to Bangkok had to make a U-turn back to Kuala Lumpur International Airport on Monday after experiencing a “pressurization issue.”

It said the pilots initiated an emergency descent although cabin altitude was not exceeded and passenger oxygen masks were not deployed.

The aircraft remained stable and landed safely at Kuala Lumpur International Airport, just over two hours after it departed, the airline said in a statement.

A Malaysia Airline spokesperson said flight MH780 was carrying 164 passengers and 12 crew members. The spokesperson said an investigation was ongoing.