SILVERADO – White smoke continued to sputter Sunday evening from a vegetation fire that began in the morning at a green-waste facility near Irvine Lake.

Authorities initially worried that the fire could grow to 200 acres, fueled by dangerously dry and windy conditions. But as of 10 p.m., it had grown to 50 acres and was 25 percent contained, according to Orange County Fire Authority Capt. Steve Concialdi.

The blaze drew the attention of two helicopters, two planes and more than 300 firefighters from multiple agencies. One outbuilding has been damaged.

One firefighter also injured an ankle during the fight and was taken to a hospital.

Concialdi said 21 residents in the area may voluntarily evacuate their homes as a precaution. The Red Cross set up a shelter at El Modena High School.

Firefighters would monitor the fire throughout the night, Concialdi said, spreading water and foam to calm the flames. The fire is expected to be fully contained by Wednesday. Some mulch piles were still burning Sunday night.

The cause of the fire, dubbed the Baker Fire, has not been determined. It was reported shortly after 10 a.m. at Aguinaga Green Waste Inc., in the 27900 block of Baker Canyon Road near Black Star Canyon Road.

On Twitter, county Supervisor Todd Spitzer said the fire had been “sparked by mulch” and “mulch production can be self-combustible.” Concialdi didn’t rule out that possibility but said an investigation was ongoing.

Chay Peterson, a Silverado resident since 1987, sat on the hood of her car watching the fire burn Sunday afternoon near OCFA Station 15.

Peterson, 52, remembers the 2007 fire that forced evacuations and destroyed many homes in Silverado.

“This sends some people into a semipanic mode and others into a heightened awareness,” Peterson said.

Peterson said she has a system for prioritizing items to take when she is forced to evacuate her home.

“Animals, paperwork and family photo albums are the top three for me,” she said.

Her husband became a volunteer firefighter after the fire in 2007 and helped battle Sunday’s fire.

Diana Good, another area resident, also stopped by the station. She had received a call from the Sheriff’s Department around 11:30 a.m. informing her that residents were being evacuated.

Good said she drove home to get her three dogs and three cats, but Baker Canyon Road had been closed. Deputies had to help get the animals, she said.

“This is not so bad compared to (the fire from) three years ago,” Good said, referring to a similar fire in 2010. “We were out for two weeks with no way in because the fire went over the road. This one is localized, it’s not as windy and it’s on private property.”

Agencies participating in the battle included the OCFA, the U.S. Forest Service, Cal Fire and others.

Staff writers Tony Saavedra and Keegan Kyle contributed to this report.