Multiple fire crews responded to a suspicious structure fire Tuesday in south Cortez.

The fire occurred in a vacant building that was boarded up on the southwest corner of East Seventh Street and South Ash Street, said Battalion Chief Rick Spencer, of the Cortez Fire Protection District.

There were no injuries or evacuations.

The building was partially engulfed in flames when firefighters arrived about 8:30 p.m.

Fire crews from Lewis Arriola and Dolores districts were called in for mutual aid. Fifteen firefighters were on scene, and operations lasted until 12:30 a.m. Wednesday.

The cause of the fire is “undetermined in cause and suspicious,” Spencer said.

The investigation was turned over to the Cortez Police Department, and the case is ongoing, said Lt. Andy Brock on Friday.

Neighbors reported flames coming from the structure and said the building has been unoccupied for a while. Fire crews reacted with an “aggressive attack from the exterior,” Spencer said. “It was intense fire behavior.”

The structure sustained heavy damage, he said.

A priority was to prevent the fire from spreading to nearby structures. Interior fire conditions made it too dangerous to enter the building.

Fire engines from Cortez, Dolores and Lewis-Arriola were on scene, along with a Cortez rescue truck. The Cortez Police Department and Southwest Health System ambulance also responded.