A large explosion ripped through the Valero oil refinery near Houston in Texas late on Monday, US media reported.
Authorities instructed residents in Port Arthur on the coast of the Gulf of Texas not to leave their homes and to keep windows and doors closed.
Local broadcaster KFDM reported a large cloud of black smoke rising from the blast. No injuries were immediately reported.
A police officer told broadcaster Fox News that the cause of the blast was thought to be an industrial heater.
According to company data, the refinery processes around 435,000 barrels of crude a day into diesel, petrol and jet fuel.
