RENO — Overnight rain helped firefighters keep the 3,400-acre Little Valley Fire from spreading in the Washoe Valley area of Nevada, according to Sierra Front Interagency Dispatch Center.

The fire sparked at about 2 a.m. PT on Friday and burned 22 homes and 17 outbuildings, Sierra Front said in a news release Sunday. It threatened 500 structures and injured four people.

The fire was 20% contained Sunday morning with 855 firefighters, 125 engines and 14 hand crews still on the scene. Crews saved 480 homes from burning in the fire area, Sierra Front said.

A flash flood watch was issued and travelers were asked to avoid the area. Residents were being contacted by the Washoe County Sheriff’s Office when it was safe to visit their homes.

Although the rain helped reduce the main fire threat, people could continue to see smoke billowing from the area, Sierra Front said.

Firefighters were mopping up around structures to ensure returning residents could enter their homes safely. Crews also worked to improve the fire line perimeter.

Meanwhile, a portion of the roadway below 6190 Franktown Road remained closed, while the roadway above that address opened. Authorities also opened U.S. 395, according to Sierra Front.

Multiple structures were still threatened. The Evacuation Center at Depoali Middle School was closed but remained equipped. Meanwhile, the Equestrian Center at the University of Nevada, Reno campus and Fuji Park in Carson City were open to temporarily house large animals.

The cause of the fire is under investigation.

Follow Marcella Corona on Twitter: @Marcella_Anahi