MANILA - At least 18 bodies were recovered and 24 people remained missing after an inter-island ferry sank early Monday in waters off Basilan province in the southern Philippines, authorities said.

The Philippine Coast Guard (PCG) said at least 317 passengers and crew were rescued following the sinking of the M/V Trisha Kerstin 3 before 2 am local time off Baluk-Baluk Island in the municipality of Hadji Muhtamad, along the Sulu Sea.

The ferry was carrying 332 passengers and 27 crew members and was en route to Jolo Island in Sulu province from Zamboanga City when it went down, the PCG said.

PCG Commandant Admiral Ronnie Gil Gavan told reporters in Manila that the vessel departed Zamboanga City port at around 9:20 pm on Sunday.

"The search and rescue operation is ongoing, but what I can say is that the ship is not overloaded," Gavan said. "It has a maximum passenger capacity of 350, and the actual passengers on board, as declared by the master, are 332."

Authorities have yet to determine the cause of the sinking.