ARLINGTON, TEXAS (CBSDFW.COM) — Two firefighters are being treated for heat exhaustion after putting out an Arlington apartment fire Sunday afternoon.

The fire started just after 4 p.m., and it quickly grew from two to four alarms — with flames so intense, that a roof at the Springfield Crossing apartments partially collapsed.

And with the heat index already at 105 degrees, firefighters struggled to deal with the heat of the flames, as well as carrying around their gear. The department eventually called in extra help.

The Arlington Fire Department said 12 units of the apartment complex are either destroyed or have some type of damage, and 30 people are looking for another place to stay.

No residents were hurt, but the cause of the fire is still under investigation.