Bangkok: A corvette sank overnight in choppy waters in the Gulf of Thailand, leaving 33 marines missing. On Monday, the Thai military sent out warships and helicopters to search for the missing marines.

The HTMS Sukhothai warship experienced an engine failure and went down just before midnight, about 20 nautical miles off the coast. Three navy vessels and two helicopters were dispatched to search for the missing.

An overnight rescue mission in bad weather secured 73 of the 106 people aboard, the navy said, with the remaining 33 forced to abandon ship.

A group of people wearing orange vests were seen leaving a ship in the dark as waves grew around it, as seen in pictures and video the navy posted on its Twitter account. How many rafts had been deployed was not immediately apparent.

According to navy spokesman Admiral Pogkrong Monthardpalin, the Sukhothai, a U.S.-built corvette in service since 1987, was struck by powerful waves on Sunday, causing it to tilt to one side and fill with water.

The navy released a photo of the gray ship on its side, and another image from a scanner screen showed the ship's bow and a gun turret sticking out of the water as it sank.