The Indonesian coast guard seized two oil tankers, an Iranian-flagged MT Horse and the Panamanian-flagged MT Freya vessels over suspected illegal oil transfer in the country’s waters on Sunday.
Coast guard spokesman Wisnu Pramandita said the tankers, seized in waters off Kalimantan province, will be escorted to Batam island in Riau Island Province for further investigation.
“The tankers, first detected at 5:30am local time concealed their identity by not showing their national flags, turning off automatic identification systems and did not respond to a radio call,” Wisnu said in a statement on Sunday.
Wisnu said that the ships were “caught red-handed” transferring oil from MT Horse to MT Freya when they were discovered by the authorities and there was an oil spill around the receiving tanker.
He added that 61 crew members from both vessels have been detained.
The International Maritime Organization requires vessels to use transponders for safety and transparency. Crews can turn off the devices if there is a danger of piracy or similar hazards. But transponders are often shut down to conceal a ship’s location during illicit activities.
Both tankers are capable of carrying 2 million barrels of oil, were last spotted earlier this month off Singapore, shipping data on Refinitiv Eikon showed.
Very Large Crude Carrier (VLCC) MT Horse, owned by the National Iranian Tanker Company (NITC), was almost fully loaded with oil while VLCC MT Freya, managed by Shanghai Future Ship Management Co, was empty, the data showed.
Iran has often been accused of concealing the destination of its oil sales by disabling tracking systems on its tankers, making it difficult to assess how much crude Tehran exports as it seeks to counter U.S. sanctions.
Iran sent the MT Horse vessel to Venezuela last year to deliver 2.1 million barrels of Iranian condensate.