SAN JOSE (CBS SF) — An arson suspect was in custody and evacuated residents allowed to return to their homes Thursday night after a series of small intentionally set fires burned 80 acres of tinder-dry vegetation near a San Jose water treatment plant.

Cal Fire reported at least six small fires in the area of Colleen Drive and Chesbro Avenue near the Santa Teresa Water Treatment Plant shortly before 6 p.m.

Shannon East was at the dog park when she says she saw a man appear to be lighting small fires in the dry brush above her neighborhood. She and two friends ran toward him.

“One of my friends was yelling, ‘Get out of there! Stop it, you’re setting fires! What are you doing?'” East said. “He had a machete. At first we thought it was a stick, but it was a big, sharp object that looked like a machete and he was down, lighting the brush.”

Some of East’s other friends knocked on doors, letting people know the flames were approaching. The fire department ordered evacuations for a small area.

San Jose Deputy Fire Chief Michael Van Elgort said about 120-150 firefighters had rushed to the scene to contain the spread of the fires. Officials said the fires were about 20% contained and 90 acres had been burned as of 10:20 p.m.

“The wind is starting to pick up,” Van Elgort said. “It’s been a hot day. Fuel is starting to pile up. Citizens need to stay away from this area.”

Firefighters on the scene were from Cal Fire, San Jose Fire Department and neighboring agencies. Air tankers and helicopters also dumped fire retardant on the smoldering blazes.

Firefighters at the scene of a grass fire near the Santa Teresa Water Treatment plant, June 4, 2020. (Steve Guerrero)

San Jose police officers had gone door-to-door earlier in the day, alerting residents along Greystone Road near the water treatment plant that they needed to evacuate.

“At this time those homes are not immediately threatened,” Van Elgort said. “But there is a risk so we want to get the people out while we have time.”

Those residents were allowed to return to their homes around 9:30 p.m.

Police have reportedly arrested at least one person. A witness told KPIX 5 police officers detained a person near his home close to where the fires were burning.

Area resident Meguel Varda provided KPIX 5 with a photo of the arson suspect being led away by officers.

SJ arson suspect (credit Meguel Varda)

“Just caught the arsonist who started 4 fires in my back yard,” said Steve Guerrero in an email to KPIX 5. “Thank you San Jose Fire and San Jose PD for saving our houses! It’s not over but now we can sleep.”

Van Elgort said a suspect was being questioned. Witnessed told police the man was also carrying a machete.

“We have a suspect we are interviewing,” he said. “He was witnessed in the act.”

Authorities did not confirm whether the person arrested was the man seen in the photo provided to KPIX 5.

Cal Fire said firefighters will be out at the scene overnight and crews would likely still be working the area Friday.

Joe Vazquez contributed to this story.