(CNN) -- Police in the Northern California town of Tracy are pursuing hundreds of possible leads in the disappearance of 8-year-old Sandra Cantu, a police spokesman said Wednesday.
Sandra Cantu, 8, disappeared on Friday, according to police in Tracy, California.
Police have received 477 tips since she disappeared Friday, 100 of them on Tuesday alone, Lt. Jeremy Watney of the Tracy Police Department told reporters.
"We're following up on all of them," he said. "It's extremely frustrating. We want her back safe. That's the bottom line.
"At this point, everything is still open."
Authorities Tuesday afternoon impounded and searched a car -- the fourth one to be seized -- that was parked near the mobile home park where Sandra lives and was last seen.
On Monday night, Tracy police and FBI agents searched six locations, some in the Orchard Estates Mobile Home Park and some in Tracy. All of the places were connected to two men who live in the mobile home park, officials said. Watch CNN report on Sandra's disappearance »
Authorities have not called the men suspects and have not named them publicly. They did not say how or if they might be related to the case.
On Friday afternoon, Sandra came home from school, kissed her mother and left to play with a friend who lives a couple of homes away. A short time later she left that home to go to another friend's home, a spokeswoman for her family said Tuesday.
The girl, who was wearing a pink Hello Kitty T-shirt and black leggings, has not been seen since, said the spokeswoman, Lisa Encarnacion.
Her parents reported her missing about 8 p.m. Friday.
Officials said surveillance camera footage recorded the girl playing in the park.
A dozen agencies are involved in the search. The number of searchers swelled over the weekend, and a similar effort is likely Saturday and Sunday, Watney said.
Police have said they doubt she ran away.
The mobile home park has fewer than 100 units. There are about 80 registered sex offenders living in a five-mile radius around it.
Tracy is about 60 miles east of San Francisco, California.
All About Missing Children