Raids resumed today on facilities of the secretive religious sect Aum Sublime Truth as Japanese news media reported that police believe the deadly nerve gas sarin was manufactured at a sect laboratory in the village of Kamikuishiki.

Police are searching for evidence that could link the sect with last week’s poison gas attack in Tokyo’s subways that killed 10 people and injured more than 5,000.

On Sunday, police carrying blowtorches and chain saws searched three buildings at the Aum compound in snowy Kamikuishiki, 65 miles southwest of Tokyo near the foot of Mount Fuji. They discovered a chemical production plant hidden behind a wall in one of the buildings, NHK Television reported.

An underground bunker targeted in the raid was being used as a warehouse, and a building with pipes coming out its side “is some kind of laboratory,” a police officer told reporters at the scene.

Specialists are investigating whether the setup and the substances found can be used to produce sarin, the gas used in the Tokyo attack.

Police also believe the sect may have been acquiring antidotes for sarin. A doctor at a hospital run by Aum bought 600 bottles of sarin antidote between October and March, NHK reported.