SAN DIEGO -- Investigators spent another day combing through refuse at a Miramar-area landfill Wednesday in hopes of finding any clue that might lead to a 2-year-old boy who vanished from a Balboa Park playground nearly a week ago.

"The most important thing to tell you right now is that we have not found Jahi (Turner)," San Diego Police Department information officer Dave Cohen said at an afternoon news conference.

MISSING JAHI TURNER Light-skinned African-American 30 pounds, 30 inches tall Black hair Wearing blue "Winnie the Pooh" T-shirt, blue pants, and gray tennis shoes INFORMATION Citizen Access Phone System: (619) 570-1070 Tip Hotline: (619) 235-8477 Download A Missing Flyer SOUND OFF Share Your Thoughts

About 80 SDPD detectives in protective, yellow body suits went through mounds of garbage in hopes of finding evidence that could shed light on the child's presumed kidnapping about 10 miles to the south.

A crew of about 40 planned to press on overnight, with a "larger contingent," including about 100 local Marines, taking over first thing Thursday morning, Cohen said during the briefing at the municipal dump.

"We will continue to be here for 24 hours a day, as long as it takes to get through the area that we want to have a chance to look at," he added.

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Police: We'll Be Here As Long As It Takes Landfill Search A Massive Undertaking

Meanwhile, authorities decided that a person they had questioned in the case was not the stranger the boy's stepfather reported seeing just before the toddler disappeared from the city's landmark downtown open-space preserve.

"We now believe that the woman we did contact was not in the location Mr. (Tieray) Jones described the woman he saw as being," Cohen said.

The mysterious park-goer whom Jones, 23, described remains a much-sought-after potential key witness in the case, the spokesman said.

"So we are pleading with this woman, whoever (she) is out there, to in fact come forward, to give us a call," he added.

Jones told police he left the boy with the woman and two other children while walking a few hundred yards to a soda machine about 2:15 p.m. last Thursday.

When he returned to the lot off 28th and Beech streets 15 minutes later, his stepson was gone, along with the others, he reported.

SDPD officials have repeatedly said they have identified no suspects in the apparent kidnapping.

Overcome with grief as she appeared on national network morning shows Tuesday morning, Jahi's 18-year-old mother, South Park resident Tameka Jones, appealed to viewers to assist in finding her son.

"Please help us if you know anything," she said. "Just help bring him back home."

Hours later, the woman went before local news cameras, this time with her husband, for a live statement outside a newly established search headquarters at a Golden Hill social club.

Jahi's stepfather urged the public to continue searching for the toddler and other missing children.

His wife then issued a direct plea.

"We just want to tell the person who has our son that you can just drop him off at a safe place so that someone who is caring can bring him home to us," she said. "We don't care who the (abductor) is, just -- we just want Jahi back."

Jahi is a light-skinned African-American, about 30 inches tall and weighing 30 pounds. At the time of his disappearance, he was wearing a blue long- sleeved T-shirt with a rendering of the "Winnie the Pooh" cartoon character on it, blue nylon pants with an orange drawstring and gray Michael Jordan tennis shoes.

Officials urged anyone with information in the case to call the SDPD's Central Division "juvenile hotline" at (619) 744-9521 or San Diego County Crime Stoppers' anonymous tip service at (619) 235-8477.