Modesto police using sonar apparently detected something of interest in San Francisco Bay during another search there in the Laci Peterson investigation.
Whatever the sonar detected had not been retrieved, and investigators did not know what it was, according to Gene Ralston, who said Wednesday that police hired him to help in the search.
"There's all kind of stuff on the bottom," he said. "I don't know if it's anything to get excited about."
Detective Doug Ridenour explained why police returned to the bay: "It's another logical area in their investigation that they need to search."
He added: "It's not any break in the case," which police officials last week reclassified as a homicide.
It started as a missing person case Christmas Eve. Scott Peterson, 30, said he last saw his wife at 9:30 that morning when he left to go on a solo fishing trip on the bay.
In early January, when the investigation first turned to the bay, sonar directed divers to a mystery object that turned out to be an anchor in the muddy bottom near the Berkeley Pier.
For that search, police used sonar from the San Mateo County Sheriff's Department.
Police returned with sonar equipment from Ralston and Associates of Idaho, according to Ralston, the owner.
Sonar can detect the shapes of objects in deep water. It was used in June in the successful search for several bodies that had been dumped in New Melones Reservoir, on the Tuolumne-Calaveras county border, in an alleged kidnap-for-ransom scheme stretching from Los Angeles to Russia.
Wednesday, police centered their bay search in the area northeast of Brooks Island, off Richmond; Scott Peterson said he went fishing around that island on Dec. 24.
Ralston said police were expected to be back in the area today, weather permitting.
"We are checking out information that may indicate something," he said. "We don't know."
Ridenour said he commented on the search only because reporters spotted the police operation on Wednesday. He would not say how long police had been back at the bay.
Wind rocked the search boats late Wednesday afternoon, and the search team returned to the Richmond Marina.
"We are going to keep searching just like we have been," Sgt. Ron Cloward said. "How many more days we'll be here, I really couldn't tell you."
Units from the San Francisco Police and Tuolumne County Sheriff's departments joined Modesto police officers and divers on Wednesday.
The effort involved four boats, some carrying dogs.
In previous exploration of the bay, police used specially trained dogs that can smell cadavers in water.
The search has taken in reservoirs and waterways from the foothills to the bay.
Cloward said it has been frustrating"not finding much of anything."
Peterson, 27, was eight months pregnant when she disappeared. Her due date passed in mid- February.
"We still hold the hope of locating her alive," Cloward said.
Sacramento Bee staff writer Herb Sample contributed to this report.
Bee staff writer Patrick Giblin can be reached at 578-2347 or firstname.lastname@example.org.