PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - An oil tanker sank in Johor waters after an explosion on board and six of its Indonesian crew members are missing.

The Malaysian Maritime Enforcement Agency (MMEA) said it received information on the incident from the Singapore Police Coast Guard (SPCG) at about 5am on Thursday (June 15) that the MT Putri Sea, which is registered in Equatorial Guinea, could not be contacted by the tanker's agent.

It said the incident could have happened 4.6 nautical miles south-west of Tanjung Pengelih in Johor.

MMEA deputy director-general (logistics) Maritime Rear Admiral Datuk Mohd Taha Ibrahim said the agency sent a patrol vessel from Tanjung Sedili to investigate.

He added that the Penggalang 15 reached the area at 6.15am and found the tanker not in sight, but there were traces of an oil spill in the area.

A search and rescue operation involving four boats was activated at 12.30pm Thursday, Admiral Mohd Taha said.

"MT Putri Sea is believed to have been carrying crude oil and was registered at Malabo Port, Equatorial Guinea. The ship is 46.3 meter long and had a crew of six - all of whom were Indonesian aged 28 to 39," the MMEA said in a statement.

The missing crew members have been identified as Akhmad Faharuddin, 35, Muhamad Heri Hernanda, 28, Raden Abdur Rahem, 31, Rendy Alamanda, 28, Sulkifli, 39, and Yohanis Sumari, 35.