Vietnamese crews participating in the search for the Malaysia Airlines passenger jet that went missing early Saturday have spotted two large oil slicks in the area of the Gulf of Thailand where the plane presumably crashed.

Vietnam's Civil Aviation Authority said in a statement that the trail of fuel spotted by a reconnaissance plane was between 10-15 kilometers (6-9 miles) long and was consistent with what would be left behind by a crashed jetliner.

The slicks are located south of the Tho Chu Islands in the Gulf of Thailand.

Malaysia Airlines and the Malaysian authorities have not yet confirmed that the plane with 239 passengers and crew on board went down, although the Vietnamese navy said it crashed some 300 kilometers (185 miles) from the Tho Chu archipelago.

"At this stage, our search and rescue teams from Malaysia, Singapore and Vietnam have failed to find evidence of any wreckage," the airline said in its latest incident report on the red-eye flight.

It added that the "the sea mission will continue while the air mission will recommence at daylight" on Sunday.

The Boeing 777-200 left Kuala Lumpur at 12:41 a.m. Saturday and was scheduled to arrive in Beijing six hours later.

Malaysia Airlines said the majority of the passengers - 154 - were either Chinese or Taiwanese. EFE