At least six people were killed in an explosion at a chemical factory in Czech Republic on Thursday, the BBC reported. Several people sustained injuries in the blast. The cause of the explosion is yet to be ascertained.

The explosion took place at a facility owned by oil distributing company Unipetrol in Kralupy nad Vltavou town. “We have received information about six dead and several others seriously injured,” regional fire service spokesperson Vladimira Kerekova told CTK news agency.

The town’s mayor, Petr Holecek, said the blast occurred in a tank holding an unspecified substance. He ruled out any risk of danger to residents in the area, The Washington Post quoted a Czech Public TV report.

Unipetrol is one of the largest oil distributing companies and producer of plastic in the Czech Republic. The facility produces toughened polystyrene, synthetic rubber for shoes and sports equipment.