Electric semi trucks on fire in Phoenix: 'Foul play is suspected'

Several electric semi trucks caught fire in an industrial area near 40th Street and Broadway early Friday morning, triggering a large response from HAZMAT crews in Phoenix and Tempe.

"I just heard an explosion, and I came out, the semis were all on fire," said John Frank.

The lithium-ion battery fire is burning at the Nikola Corporation building, and officials are calling it difficult and tricky to fight. A thick black smoke and a strong chemical smell could be sensed in the area.

The explosion was caught on camera, and according to fire officials, four trucks are on fire. As a precaution, fire officials said the Nikola Corporation headquarters we re evacuated while crews battled the blaze.

Officials say there was some kind of chemical reaction in a truck's battery that sparked a fire, and this spread to other vehicles.

According to the Nikola Motor Company, foul play is suspected. The company says a vehicle was seen near the trucks right before the flames sparked.

‘Very difficult’

Firefighters have been spraying water over the battery fire, but if they stop, they say the flames will reignite. 

"So these cells that are packed in these batteries, they contain a lot of energy in a small amount of space, so extinguishing these are very difficult," said Capt. Todd Keller with Phoenix Fire. "[What] we're doing right now is that we're cooling these trucks down and preventing extension."

Typically, crews would put sand over this type of fire to extinguish it. They cannot do that in this case because the semis are so big, so they're spraying as much water as they can to cool down the vehicles.

Around 50 firefighters are responding.