Several vehicles were in flames after an explosion rocked the center of Italy’s second city Milan, writes DW.

The incident appears to have been the result of an accident and there are no known fatalities. Mayor Giuseppe Sala told reporters the van where the blast originated was carrying oxygen cylinders and that the explosion was not due to terrorism or crime.

Witnesses in the city’s Porta Romana neighborhood reported the loud explosion at about 11:45 a.m. and saw a plume of black smoke.

The Reuters news agency said that one person had been injured in the blast, but that there were no known fatalities.