ANTIOCH, California (CNN) -- Investigators have found bones on the property where kidnapping suspects Phillip and Nancy Garrido lived for 18 years with Jaycee Dugard and her two daughters, police said Wednesday.
Police search for evidence relating to missing girls Ilene Misheloff and Michaela Garecht.
More bones of undetermined origin also were found on property adjacent to the home, Lt. Chris Orrey of the Hayward Police Department said.
"We have located what appear to be bones on both properties," Orrey told reporters. "We can't tell at this point if those bones are human or animal."
The evidence has been sent to a laboratory for analysis, Orrey said.
Searchers were looking for evidence linking the Garridos to the disappearances of Michaela Garecht in 1988 and Ilene Misheloff in 1989.
Hayward Police executed a search warrant Tuesday in connection Garecht's case. She was 9 when she was last seen, police said. Watch police search the Garrido home »
In addition, police in Dublin, California, obtained a search warrant for the same locations in their investigation of the 1989 disappearance of 13-year-old Misheloff, police said.
Both warrants were executed simultaneously Tuesday, near Antioch, California, in unincorporated Contra Costa County, east of San Francisco.
Investigators will continue Thursday to remove debris in anticipation of using search dogs and ground-penetrating radar, Orrey said.
About 75 percent of the debris on the Garrido property has been searched for possible evidence, she said. Three truckloads of trash, debris and trees have been carted away, but another eight to 15 truckloads remain, she said.
"We haven't found anything that breaks open our case," she said.
Garecht's mother said Tuesday that she holds out hope that her daughter will be found alive.
"I know that if Jaycee Dugard can be found alive and come home after 18 years, then my daughter can be found alive and come home," Sharon Murch told reporters at a news conference. Learn more about Phillip Garrido's history »
The Garridos face a combined 29 felony counts in connection with the 1991 kidnapping of Dugard, then 11, from South Lake Tahoe, California.
Authorities believe the couple held Dugard in a well-hidden compound behind their home for 18 years and have said Phillip Garrido, a registered sex offender, fathered two children with Dugard. The Garridos live near Antioch, California, in unincorporated Contra Costa County, east of San Francisco.
Police from both agencies said that while Garrido has not been named a suspect in the other abductions, he cannot be eliminated as a suspect in either case. Neither police department has interviewed Dugard, police said.
Garecht was abducted by a stranger in front of a market in south Hayward on November 19, 1988, according to Murch's Web site on her missing daughter, MissingMichaela.com.
Over the past two decades, police have followed some 13,000 tips in investigating her disappearance, Orrey said.
She said Hayward police have also noted similarities between the Garecht and Dugard cases. The victims were similar in age and appearance, Orrey said, and both were abducted in daylight, in a "brazen" manner.
The suspect vehicle in the Garecht case is also similar to the sedan found on the Garrido property, she added, and in pictures from that time, Garrido appears to resemble a sketch of a suspect based on a witness description.
Murch said she also noticed the similarities in their cases and thought it could lead to finding her daughter.
"My first thought when I heard Jaycee was found was please, God, let Michaela be with her," Murch said.
Misheloff failed to make it home from school on January 30, 1989, Dublin Police Lt. Kurt von Savoye said.
"For 20 years, we have been attempting to determine what happened." There is no eyewitness that could say with certainty she was abducted, and evidence in the case was limited, he said.
A witness did report seeing Misheloff getting into a vehicle, a sedan similar to one found on the Garrido property, at the time of her disappearance, von Savoye said. Garrido "has demonstrated a propensity to abduct young girls," police said in a statement, and he was released from prison a few months before Misheloff disappeared. Dublin is about 40 miles from Antioch.
Misheloff's family is aware of the search warrant execution but are out of town on a family emergency, von Savoye said.
In the property search, there are no current plans in place to raze structures, Orrey said, but "we are very interested in what might be behind walls, under flooring, under the ground." Authorities are prepared to disassemble structures if needed, she said.