Few Clues In Laci Peterson Search

California officials say it now appears that a missing pregnant woman may have left her home in a car -- not by foot as previously thought.

Laci Peterson's husband reported her missing December 24th after he returned from a solo fishing trip.

Modesto police brought in a bloodhound to try to track the woman -- and the dog led them to a road.

The Modesto Bee reports underwater search and rescue teams yesterday explored a section of river after the dog headed in that direction.

Hundreds of volunteers are now involved in the search for the 27-year-old.

Investigators grasping for leads in the disappearance of Laci Rocha Peterson say they are contacting known sex offenders in her Modesto neighborhood.

Family and friends are holding a candlelight vigil for her Tuesday afternoon in a park.

Meanwhile, police are urging residents to search rural areas where the woman may have been walking her dog before she disappeared Christmas Eve.

On horseback, by boat and in the air, it's a search made more urgent by the fact that Peterson is eight-and-half months pregnant, reports CBS News Correspondent Sandra Hughes. Over the weekend, an anonymous donor boosted the reward to half a million dollars.

"Take the money and bring my daughter back safe," said Dennis Rocha, Peterson's father. "Take the money and get away free. Get out of here. Go with the money — take the reward and go."

Peterson was last seen by her husband Scott, who said she was going to walk their dog while he headed off to go fishing alone. A neighbor found the dog wandering around with the leash still on.

"We're going to find her, we're going to bring her home," vowed Renee Tomlinson, a friend.

The 27-year-old was described by friends and family as the life of the party, and very happy in her marriage.

"No motive, no family history, they were doing awesome, looking very forward to having their baby," said Brent Rocha, her brother.

While police won't call her husband a suspect, they have impounded the family cars and searched his boat and the marina where he went fishing.

Investigators returned to the Berkeley Marina for the third time Monday. Police have found a boat launch slip and a gasoline receipt.

Police are examining a possible connection between Peterson's disappearance and a burglary across the street from her home, reports John Lobertini of CBS affiliate KPIX-TV. Susan Medina was burglarized sometime between Christmas Eve morning and late on December 26, and she thinks that maybe Peterson saw something that put her in danger.

"It's just too much of a coincidence," said Medina.

Some of the items taken from the Medina home included a safe containing $50,000 in jewelry.

Police were also looking at surveillance videotape from a sporting goods store on the north end of Modesto. There were reports that Peterson may have been seen there on Christmas Eve. But investigators said that was still unconfirmed.

Peterson's friends and family have saturated the community and the Internet with pictures and pleas for help, galvanizing hundreds of volunteer searchers. But after six days, police say they don't have one concrete clue about what happened to Peterson.