Czech firefighters were battling a major chemical blaze in eastern Czech Republic on Friday after a freight train derailed and carcinogenic benzol from damaged tank wagons caught fire.

The derailment took place near the station in the town of Hustopece nad Becvou around noon local time, with the fire sending thick black smoke into the air visible from a long distance. The cause of the derailment was under investigation.

No one has been injured.

The nearest houses in the town are located about 500 meters from the fire, but the smoke hadn’t reached them.

Firefighters said that 15 of the 17 tanks in the train were on fire. Each tank contained about 60 metric tons of the toxic substance. They used a helicopter to contain the fire while their counterparts from neighboring Slovakia were on the way to help.

Authorities said that no levels of dangerous substances exceeding limits have been detected in the town, but advised that residents there and in nearby towns and villages don’t open their windows, and stay indoors.

Benzol contains benzene, toluene, and xylene, which are used to make various chemical substances.