Firefighters battling massive fire at commercial structure in Fontana

Firefighters are battling a massive fire at a commercial building in Fontana. 

The blaze was first reported at around 8:30 p.m. at a pallet yard in the 1500 block of Whittram Avenue, according to San Bernardino County Fire Department officials. 

Crews reported that about a quarter-acre of stacked pallets were "well involved with exposures," and that multiple power poles were also involved. 

As the firefight continued, 13 engines, five trucks and about 70 firefighters were on the scene of the fire. 

"If you are in the area, please stay indoors due to smoke and air quality concerns," firefighters said on X. 

No evacuations have yet been ordered. 

The cause of the blaze remains under investigation. 

This is a developing story. Check back for details.