Hundreds of tips have been pouring into the Tracy Police Department about an 8-year-old girl missing since Friday.
Officers are also working around the clock in an effort to find Sandra Cantu, who was last seen walking in Orchard Estates Mobile Home Park.
There are 150 to 200 people working on the case, Lt. Jeremy Watney said. Officers are working 12-hour shifts and putting vacation days on hold to accommodate the investigation.
The San Jose Mercury News is reporting Volunteers and police searched a Tracy dump Wednesday as they search for evidence in the case.
The paper said police wanted to search the dump "for information about the case."
A reward for information leading to Cantu's return has grown to $7,000.
One of the people looking for Cantu is Midsi Sanchez. She is the little girl who was kidnapped by Curtis Dean Anderson back in 2000 when she was 8 years old.
Sanchez told the Times-Herald, "My background obviously, I saw that and everything came back. I wondered what she must be going through; what this is doing to her family."
Sanchez put up fliers with pictures of the missing child over the weekend. She told the paper she is also trying to get in contact with the family.
Cantu was last seen Friday afternoon walking from her home to a friend's home within the park, located just off West Clover Road.
Authorities have searched five properties in Tracy -- including four mobile homes in the park -- as well as a location in Oakdale.
Three cars were seized in the investigation, police said.
There's nothing to indicate the girl is in Mexico, police said, but it's unclear if Daniel Cantu is still in the area. He told officials that he may not be going back to work in Southern California.
Police are looking at everybody involved in the case, Watney said, and family members have not been dismissed. Nobody has been cleared in the case, police said.
Officials are focusing their search on two men who live in the mobile home park where Sandra Cantu lives, authorities said earlier in the day.
Frank Wohler, a martial arts professor at Delta Kajukenbo who lives in the park, said he had no part in the disappearance.
Wohler admitted that two years ago after he moved to the park, he kissed Sandra Cantu on the lips "to be nice."
Officials took some items from Wohler's home, but it's unclear what they were. They also searched his martial arts studio in Tracy.
Wohler said "a couple CDs" were taken by police.
It's unknown if Wohler is one of the persons of interest.
A source close to the investigation expressed concern to KCRA 3, saying that the Tracy Police Department did not move fast enough to question and search registered and paroled sex offenders living nearby.
A search on the Megan's Law database shows that there are 12 registered sex offenders living within a mile of where Sandra Cantu disappeared. Of those 12, eight were arrested on charges of lewd acts with a child, three were found guilty of forcible rape and one had contact with a minor with intent to commit a sexual offense.
Sandra Cantu is 4 feet tall, weighs 45 pounds and has brown hair and brown eyes. She was wearing a pink Hello Kitty T-shirt and black leggings. KCRA.com contributed to this report.