Six million gallon asphalt fuel tank explodes

GRANITE CITY, Ill. (CNN) -- A tank holding 6 million gallons of asphalt fuel exploded Tuesday afternoon, belching flames and thick black smoke into the air as firefighters stood by helplessly. Nearby roads were closed because of the smoke.

"We're not going to be able to put this fire out," said Granite City Police Lt. Ned Tapp. "We're going to let this tank burn out."

No injuries were reported, Tapp said. Police got the call at 12:51 p.m. CDT (1:51 p.m. EDT).

"We're very lucky that no one got injured," he said of the explosion in the Tri-City Port Authority, just across the Mississippi River from St. Louis. Tapp said it's not known what caused the blast.

He said emergency crews were hosing off tanks next to the burning tank to keep them cool and try to prevent them from catching on fire.

Police closed down two miles of Route 3, the main highway in the area, as well as several other side roads in the mostly industrial area. Authorities have told residents nearby to remain in their homes, although Tapp said it's not believed the smoke is toxic.

He predicted the tank would burn until sometime Wednesday. Tapp said crews will remain nearby to keep an eye on the blaze.

Asphalt fuel is an oil-based compound that is used to make asphalt, shingles and other products.