New York (CNN) -- Police said Thursday that they are nearly done with at least one part of a search effort in which investigators scoured a remote stretch of beach in Long Island, New York, where the bodies of eight prostitutes were found.
"We've almost completed a very exhaustive methodical search of wooded areas, brush areas and beach areas from Oak Beach to the Nassau County line," Suffolk County Police Commissioner Richard Dormer told reporters.
Dormer said K-9 units and dive teams had been added to the search operation since December in an effort to locate Shannan Gilbert, who had been missing since May and was last seen alive in the Gilgo Beach area.
"Our search for her will continue, even though this component of the search is nearly over," Dormer said, promising investigators would be back.
Gilbert's sisters told CNN that Shannan was an escort who was visiting a client a few miles away from Gilgo Beach. They said that for some reason, Shannan ran from his house and called 911, saying that someone was trying to hurt her. Several neighbors also called 911. Witnesses say police came more than 30 minutes later. By then, Gilbert was gone and has never been heard from again.
"You want to believe everything was OK with her," Sherre Gilbert said. "But at the same time, so much time has passed it's impossible to really think that she is still alive."
Earlier this week, police discovered the remains of three more women. A woman's body was also found on March 29 off Ocean Parkway, west of Cedar Beach.
Police say the hunt for a potential serial killer continues, as does the search for Gilbert. She, like the women whose bodies have been found, advertised for prostitution services on sites such as Craigslist.
The first four bodies were discovered stuffed into bushes on a quarter-mile stretch of waterfront property on Oak Beach, indicating "they were dumped there by the same person or persons," said Dormer in December. "It's too coincidental that there were four bodies in the same location."
The remains of a fifth body were found about a mile from where the other corpses were discovered, he said, refusing to disclose exactly where the three additional remains were found on Monday.
Sherre Gilbert said even if her sister isn't ever found, the search has led to one positive outcome: the discovery of eight other women.
"It's a great thing that she did for other people and I'm just really hoping and praying, I pray every day about, I hope that one day she will be found and that the killer will get what he deserves, which is to spend the rest of his life behind bars," Gilbert said.
CNN's Kaj Larsen and Jen Christensen contributed to this report