At least six people were forced to evacuate after a fire sparked Sunday evening at a Northeast Side apartment complex, Assistant Fire Chief Wesley West said.

More than a dozen San Antonio Fire Department first responders helped extinguish flames that engulfed four apartment units around 6:30 p.m. in the 14900 block of Nacogdoches Road, West said.

The affected units had "significant fire damage." Although West said he was not sure what caused the fire, the assistant chief believes it started on the second floor of the apartment complex.