A chemical spill and flash fire at a Downtown Denver brew pub has forced the evacuation of the building and is knotting up traffic this morning.

The accident happened at about 7:15 a.m. at the Rock Bottom Restaurant and Brewery, 1001 16th St., said Capt. Craig Carter, a Denver Fire Department spokesman.

The fire is out and there were no injuries, Carter said. Emergency medical workers were on scene, but weren’t treating anyone.

On Tuesday there was a spill of chlorine dioxide, which is used to clean empty beer tanks, at the brew pub, Carter said. It was mopped up and the spill didn’t cause a problem until this morning when a worker dropped a keg. A spark from the keg ignited remnant residue of the spill and fueled a flash fire.

The fire department’s hazmat team is on scene and is flushing any residue left from the spill to ensure an incident like this doesn’t happen again, Carter said.

A decontamination tent was set up on Curtis Street as a precaution.

Several fire engines and at least a dozen firefighters in hazmat gear responded.

The flash fire released a plume of smoke and firefighters were concerned that it may have been toxic. Tests by the hazmat team determined that no harmful toxins were released, Carter said.

Police and firefighters shut down Curtis Street from 15th to 17th Street for a time as the fire and chemical residue was mopped up.

Workers with Rock Bottom, who were waiting along Curtis Street for the business to reopen, declined comment.

A parking garage for Independence Plaza was not accessible because of the Curtis Street closure. Several other storefront businesses along the block were closed this morning, as were several offices directly above the brew pub.

The free 16th Street mall shuttle remained open.

Tracey Weil, an artist working on an architectural project, was suppose to be in a business meeting at 8:30 but was shut out because of the incident.

“I’m sitting here waiting,” Weil said from a perch on the 16th Street Mall. “I tried to call, but no one is answering the phones.”

Instead, Weil people watched and surfed the web on his smart phone.

“It’s kind of nice to sit out here and relax,” Weil said. “What can you do? You just have to hang out.”

Kieran Nicholson: 303-954-1822 or knicholson@denverpost.com.