SIERRA MADRE – A wildfire that by Sunday had scorched more than 400 acres and forced the evacuation of 1,000 people could take four to seven days to contain, officials said.

The Santa Anita Fire – which has also been referred to as the Santa Anita Canyon Fire and Chantry Flat Fire – was still raging in the foothills above Sierra Madre and Arcadia on Sunday night, and was only about 30 percent contained.

Officials anticipate the fire could grow before it begins to shrink.

“Naturally, we want to hold the acreage,” said Marc Peebler, battalion chief of Southern California Incident Management Team 3, an emergency response group made up of area fire agencies.

“But because of the steep grade, it will probably grow in acreage before we get it contained.”

All private and public Sierra Madre schools will be closed today, city officials said, and people with respiratory conditions are advised to stay indoors due to the smoke.

The blaze was first reported as a five-acre fire about 3 p.m. Saturday off of Santa Anita Canyon Road near the Chantry Flat area, Peebler said.

Hours later, the fire had burned 100 acres, then quadrupled in size overnight, prompting the evacuations of about 550 houses in the northern area of Sierra Madre, he said.

Resources from the throughout the region were called to assist in the firefight Sunday, including about 400 firefighters and another 100 support personnel, officials said.