The regional Japan Coast Guard headquarters in Kagoshima Prefecture said Tuesday it has confirmed that almost 70 kg of white powder found off Yakushima Island in late June was heroin, making it the largest amount of the drug seized in the nation at one time.

The drug, worth roughly ¥2.1 billion on the street, was in 200 plastic bags snagged by a fishing net on June 26 in the sea about 5.5 km south of Yakushima's Anbo port, coast guard officials said.

The Japan Coast Guard and the Kagoshima Prefectural Police have launched an investigation, believing that someone might have tried to smuggle the drugs into Japan.

According to the coast guard, the previous record amount of heroin seized at one time was 20.6 kg in 1989. Health ministry statistics show the total amount of heroin confiscated across the nation in fiscal 2015 was about 2 kg.

Heroin is an opiate derived from morphine. It is highly addictive and the Narcotics and Psychotropics Control Law prohibits the manufacture, export, import, possession or use of the drug.