Officers apprehended the ship after it turned off its lights and increased its speed to try to flee Indonesian waters in the Tanjung Balai Karimun region, Riau Islands, according to the navy.

Officers seized nearly 100 yellow and white sacks holding about 1.2 tonnes of cocaine and 705 kilograms of methamphetamine worth Rp 7 trillion rupiah (US$425 million), Indonesian Navy spokesperson Cdre. I Made Wira Hady Arsanta Wardhana said in a statement, as quoted by Reuters.

Indonesia has among the world's strictest anti-narcotics laws and drug trafficking is punishable by death.

The navy said the ship, bearing a Thai flag, was taken to a navy base in Tanjung Balai Karimun. It did not give details of the crew members' origins apart from their nationalities.

Officials are still investigating where the drugs came from and where the ship was headed, the Navy's First Fleet Armada commander Rear Adm. Fauzi said in a press conference.

The seizure is among the largest busts in the country.

A record 190 tons of methamphetamine were seized in East and Southeast Asia in 2023 as organised crime groups exploited weak law enforcement to traffic the drugs, mainly via the Gulf of Thailand, the United Nations Office on Drugs and Crime said in a 2024 report.

The Golden Triangle, an area of northeast Myanmar that meets parts of Thailand and Laos, has a long history of producing drugs, mainly used by Asian crime syndicates which distribute the narcotics as far as Japan and New Zealand.

In 2022, 179 kg of cocaine were found in waters near the Merak port in Banten; at the time the largest cocaine seizure in the country, the UN drug agency said in a 2023 global report on cocaine.