ALLENTOWN, Pa. (CBS) – Authorities are investigating the cause of a four-alarm fire in Allentown that injured five firefighters Thursday morning.

The fire broke out at about 1 p.m. in a home at 854 N 8th Street and quickly reached four-alarm status. The blaze damaged eight row homes, displacing several families.

Five firefighters suffered heat exhaustion and dehydration. Three were transported to the hospital for treatment, and two were treated at the scene. Firefighters were pulled from the building due to danger of structure collapse.

Red Cross disaster volunteers provided assistance to four of the eight families – a total of nine adults and 15 children.

The cause of the fire remains under investigation.