Doug Stanglin

USA TODAY

A large warehouse fire erupted Tuesday near an oil storage depot in the northern city of Qazvin, Iran's semi-official FARS news agency reported.

The Mehr news agency said there were no immediate reports of casualties, but that the blaze was threatening to ignite an 18,000-liter oil storage tank.

It quoted a warehouse worker as saying the blaze was due to welding.

An Iranian agency initially said many casualties were expected, according to the Associated Press .

The city of around 1.1 million people was once an ancient capital of Persia. It is located about 100 miles northwest of Tehran.