OKLAHOMA CITY - Firefighters have put out a building fire in northwest Oklahoma City, Friday morning.

According to the fire department, crews responded to the fire just after 5:30 a.m. at a building at N.W. 23rd and Classen Boulevard. The building appears to be vacant.

Firefighters reported seeing heavy black smoke and flames shooting from the inside of the structure upon arrival. They were able to put out the fire.

The cause is under investigation.