Denver fire crews battled a blaze at a warehouse in RiNo on Tuesday.

Crews were dispatched to the warehouse at 3315 Walnut St. shortly after 5 p.m. and saw heavy smoke coming from the interior, said Greg Pixley, a spokesman for the Denver Fire Department. 

Firefighters attempted to extinguish the blaze from inside the building, but because the blaze was “so involved” and began burning through the ceiling, they were forced to call a second alarm, which brought additional crews to the scene, Pixley said.

“We don’t want to put our firefighters in a negative position,” Pixley said during a short press conference Tuesday evening.

The additional crews fought the flames from the exterior of the building and are “trying to stop the fire from extending to other structures.”

Fire officials are unaware of the current status of the building and whether anyone was inside at the time of the fire started. As of 6:45 p.m. Tuesday no injuries have been reported, Pixley said.

Residents living near the structure were allowed to return to their homes.

Investigators will begin an investigation once the structure is deemed safe to enter and fire is contained, Pixley said. 

Anyone with information regarding the fire is encouraged to contact the Denver Fire Department.