Updated

Clothing and other items belonging to a missing New Jersey prostitute whose disappearance helped spark an investigation into a possible serial killing spree on New York's Long Island have been recovered near where the woman was last seen 18 months ago, police said Wednesday.

Suffolk County Police Commissioner Richard Dormer said officers have not found any remains of 24-year-old Shannan Gilbert, who they think drowned, but said the search would resume on Thursday.

"If it wasn't for Shannan Gilbert's disappearance we may never have found the remains of the other victims," Dormer told reporters at a news conference.

Police were looking for the Jersey City, N.J., woman last December when they stumbled upon what would eventually become 10 sets of human remains in the underbrush along a beach highway on a barrier island south of Long Island. Dormer and other police officials said they do not believe the deaths of the 10 people, mostly women linked to the sex trade, and Gilbert's disappearance are related.

Detectives on Tuesday and Wednesday found the woman's pocketbook with a photo ID inside, her jeans and shoes, as well as a cellphone they believe she owned. They think she drowned after becoming upset for an unexplained reason.

"It's very easy to get engulfed with water, muck, and fall down and not be able to get out of there," Dormer said. "We surmise that's what happened to Shannan and she's in there some place and we're going to do everything we can to find her."

In a telephone interview with Newsday, Gilbert's mom, Mari Cox Gilbert of Ellenville, N.Y., said she watched the news conference on television.

"I am still doubtful," Gilbert told the newspaper. "I need to see the items for myself to believe it."

Shannan Gilbert was last seen at a client's home in Oak Beach, a gated seashore community several miles east of Jones Beach State Park. She was taken by a driver to the Oak Beach community, where she met a client for sex. The client, Joseph Brewer, was interviewed by police but is not considered a suspect, authorities said.

Brewer has told police that Gilbert became upset after about two hours and that he summoned the driver to remove her from his home. The woman then reportedly fled the house.

Oak Beach resident Gustav Colletti has told authorities that Gilbert banged on his door at around 4:45 a.m. on May 1, 2010.

"She was saying, 'I need help, I need help, they're after me,'" Coletti has told reporters. He said he told the woman he was calling police, but she immediately turned around and fled.

A few moments later, a man in a sport utility vehicle drove past the house and told Coletti he was looking for the woman. Coletti said the driver told him they had been at a party and the woman had become upset. The driver also has been interviewed but was not identified as a suspect.

Suffolk Chief of Detectives Dominic Varrone said witness reports that the woman was acting irrationally are consistent with her likely demise.

"Apparently what we found yesterday is very indicative, very supportive of the fact that she just wandered and ran aimlessly into this marshy area," he said.

While the inquiry into Gilbert's disappearance appeared to be coming to a conclusion, homicide detectives still have 10 unsolved murder cases to contend with. Police have received more than 1,200 tips about the case and have offered a $25,000 reward but have yet to identify any suspects.

Officers searched 90 specific locations in and around a several-mile stretch of Ocean Parkway on Monday; areas that were mapped after the FBI took high-tech surveillance photos of the area this year. Inspector Stuart Cameron noted that most areas had already been searched, but said the FBI surveillance photos prompted a return to the some of the sites.

The remains of the 10 people — eight women, a man and a baby — were found strewn mostly along the remote beach parkway, but some body parts from those victims were found on eastern Long Island and nearly 50 miles away on Fire Island. Police have identified only five of the 10 victims. Those five were all women working as escorts. The oldest remains are linked to a case 15 years ago.

Police Commissioner Richard Dormer has pulled back on earlier theories that multiple killers might have left the bodies along the parkway, the first of which was a woman who went missing in 1996. Dormer said last week he believes that because nine of the 10 were involved in the sex trade, their killings are likely related.

The tenth victim, a toddler girl, was linked by DNA to a woman believed to be her mother. The remains of the mother and child were found seven miles apart.