EL PASO, Texas — Five people were injured Tuesday in an explosion in the maintenance area of Sun Metro Transit Operations Center, according to the El Paso Fire Department Chief.

The transit center operates out of the El Paso International Airport, where the fire department responded to a Condition 4 fire. A Condition 4 fire typically refers to a fire occurring under extremely dangerous conditions.

A total of 48 units and more than 100 firefighters responded to the explosion.

The roof and walls of the building collapsed in due to the fire, according to officials. Billows of smoke could be seen surrounding Montana Avenue and traffic was closed in the area.

Officials wouldn’t confirm if the explosion came from a bus, but said the investigation may take a week or two due to the amount of debris.

El Paso International Airport operations are unaffected.

This is a developing story. We will update it as we get more information.