WALNUT CREEK, Calif. -- A four-alarm fire that burned through a lumber yard in Walnut Creek Saturday afternoon closed nearby streets and caused a power outage that affected more than 300 PG&E customers.

The fire was reported at 1:44 p.m. at Piedmont Lumber, located at 2860 N. Main St, Contra Costa County Fire Protection District Fire Chief John Ross said.

About 70 firefighters and other personnel responded to the fire, which was contained but still burning at 4:30 p.m. Saturday, Ross said.

He said crews are in a "long, arduous firefight" that was expected to last into the evening.

The building on the property was a complete loss, and the county's hazardous materials team was on site because hazardous materials such as paints, solvents, and petroleum materials burned in the fire, he said.

Authorities did not issue a shelter-in-place warning, but Ross said the warning was considered as temperatures decreased later that evening since "as it cools off, smoke tends to lay down more."

Following the report of the fire, PG&E crews de-energized the power circuit nearby, cutting off power to 306 customers, PG&E spokesman J.D. Guidi said.

The outage only affected customers in the area near North Main Street, Guidi said.

An employee at a Burger King restaurant located across the street from the lumber yard said the restaurant is one of the businesses without power. She said there were no customers in the restaurant, so "we're just standing by in here, and cleaning up."

North Main Street was closed between Second and Sunnyvale avenues while crews fought the blaze, according to Ross.

No injuries were reported in connection with the fire.

Employees at the North Main Pet Lodge, located adjacent to the lumber yard, appeared to suffer from minor smoke inhalation but refused care, Ross said.

Authorities took 18 dogs and two cats out of the business and transported them to the county's animal shelter in Martinez, he said.