Witnesses say there was an explosion and then fire at the site where a four story apartment building was under construction.  The apartments were being built at 800 S.E. Tech Center Drive in Vancouver.

There are no reported injuries.  It doesn't appear anyone was inside at the time of the fire.

A natural gas line helped to feed the fire.  

The fire spread fast, because the building wasn't finished.  There was no sprinkler system.

Investigators will search the rubble for the cause of the fire.

Photo: KATU-TV