Authorities spoke for a second time to a man they say admitted kissing missing 8-year-old California girl Sandra Cantu on the mouth two years ago, when she was 6.
Frank Wohler's station wagon was returned Thursday after authorities confiscated the vehicle Monday night when they searched his home.
The FBI also searched the Oakdale, Calif., home of a man related to the neighbor of the girl.
The relative, Chris Sinclair, has been a focus of the investigation into Sandra's disappearance a week ago. Three vehicles connected to him have already been seized.
Authorities widened their hunt for the child as the investigation heated up. They continued sifting through garbage at the Tracy landfill and another dump site Friday, an effort that began a day earlier.
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Also Friday, the California Highway Patrol conducted a helicopter search of the vicinity to cover a large area in a short time period, Watney told reporters.
Volunteers are also being urged to participate in an expanded search of the town over the weekend.
"Any and all help is welcome," Watney said at a morning press conference Friday.
Sandra was last seen about 4 p.m. March 27 walking away from the Orchard Estates Mobile Home Park in Tracy, Calif., where she lives with her family. Her mother reported her missing about 8 p.m. that night.
Investigators said they have been poring over about 720 leads in their search for the child, but none of the tips indicate Sandra is dead.
"We’ve had sightings from people all over California saying they’ve seen her ... which would definitely suggest that she is still alive,” say Watney. "Statistics show that she’s probably still in Tracy, but if we get a tip in Nevada or in Southern California ... wherever we get a tip, we are going to go."
Investigators combed the Old River, about three miles from the girl's home, on Thursday. They also spent the day going through residents' trash.
"Everything that comes through they're searching, garbage trucks and everything," Laurence Campiott, who works at the landfill, told FOX San Francisco affiliate KTVU.
The search of the garbage is routine, according to police.
"We are going through absolutely everybody’s trash in this city of Tracy this week," Tracy Police Lieutenant Jeremy Watney told reporters Thursday. "It’s just covering a base. If we don’t do it now, we won’t be able to do it later."
Police said another search of the trailer park where Sandra lives yielded a Hello Kitty T-shirt like the one the child was last seen wearing.
They showed the top to her mother, Maria Chavez.
"It looked very similar [to the one she wore], which is why we brought it back to the mother. But mother said it wasn't. That's not to say we're not going further," KTVU quoted Watney as saying. "We still have it. It's still going to be examined. It's still going to be tested."
The reward for information leading to the child's whereabouts has risen to about $22,000, according to police.
On Thursday, Sandra's father pleaded with her to "scream, kick, do what you need to do" to escape her captors.
Daniel Cantu said he has been questioned extensively by detectives.
"I've just gotten through a couple hours of being interrogated," he told KTVU.
Sandra's parents are divorced; her father lives along the California border with Mexico. He hasn't seen his daughter in a year, he told KTVU, but he wanted to get a message to her.
"Honey, if you can get to a phone, dial 911, babe," the station quoted him as saying. "Scream. Kick. Do what you need to do."
The child is described as Hispanic, 4 feet tall and weighing 45 pounds, with brown hair, brown eyes and a small birthmark on her right cheek. She was wearing a pink Hello Kitty T-shirt and black leggings when she disappeared.
FOXNews.com's Mariel Bird and Catherine Donaldson-Evans contributed to this report.