Vietnamese authorities searching waters for the missing Boeing 777 jetliner spotted an object on Sunday that they suspected was one of the plane’s doors.

More than a day and half after Malaysia Airlines Flight MH370 disappeared with 239 people on board, no confirmed debris from the plane had been found, and the final minutes before it went missing remained a mystery. The plane lost contact with ground controllers somewhere between Malaysia and Vietnam after leaving Kuala Lumpur early Saturday morning en route to Beijing.

Searchers in a low-flying plane spotted what appeared to be a door from the missing jet, the deputy chief of staff of Vietnam’s army, Lt. Gen. Vo Van Tuan, was quoted as saying by the state-run Thanh Nien newspaper. It was found in waters about 90 kilometres south of Tho Chu island, in the same area where oil slicks were spotted on Saturday.

“From this object, hopefully (we) will find the missing plane,” Mr. Tuan said. Two ships from the maritime police were heading to the site.

The missing plane apparently fell from the sky at cruising altitude in fine weather, and the pilots were either unable or had no time to send a distress signal unusual circumstances under which a modern jetliner operated by a professional airline would crash.

Malaysia’s air force chief, Rodzali Daud, said radar indicated that before it disappeared, the plane may have turned back, but there were no further details on which direction it went or how far it veered off course.

“We are trying to make sense of this,” Daud said at a news conference. “The military radar indicated that the aircraft may have made a turn back, and in some parts this was corroborated by civilian radar.”

Malaysia Airlines Chief Executive Ahmad Jauhari Yahya said pilots are supposed to inform the airline and traffic control authorities if the plane does a U—turn. “From what we have, there was no such distress signal or distress call per se, so we are equally puzzled,” he said.

A total of 34 aircraft and 40 ships were deployed to the area by Malaysia, Thailand, Australia, Singapore, Indonesia, China and the United States, in addition to Vietnam’s fleet.

More In: World | International