CHICO, Calif. -

Firefighters battled massive flames at a Chico townhouse building Monday.

The complex, Manzanita Gardens, is located on the 1400 block of Manzanita Avenue behind Pleasant Valley High School.

Witnesses said they heard several explosions about 4:45 p.m. coming from the complex.

The building was fully engulfed when firefighters from both the Chico Fire Department and CAL FIRE arrived.

Tina Fraga, a woman at the scene, described what she saw after hearing the explosions.

“I was sitting in my chair and my husband came running down the stairs telling me ‘there’s a fire in the backyard’ so I went to check,” Fraga said. “There was a big plume of black smoke, then six to ten explosions. I told my husband to call 911.”

The cause of the fire is still under investigation, but Fraga said it could be human-caused.

“A guy said his son had started the fire,” Fraga said. “He didn’t know what the cause of it was.”

No injuries have been reported.

Manzanita Avenue is closed between Ceanothus and Madrone Avenues.