Authorities plan to expand their search Monday beyond the South Shore barrier island where police have found several human remains since December.

Starting about 9 a.m., New York State Police will search both sides of the Wantagh State Parkway from Merrick Road to Ocean Parkway, the agency said Friday.

The portion of the parkway between Merrick Road and the Jones Beach water tower -- including the bike and pedestrian path -- will be closed "for an indeterminate amount of time," police said.

State Police Lt. William Hulse said the search expansion was not triggered by new leads.

Since December, police have conducted several canvasses of the area to look for 24-year-old Shannan Gilbert, a prostitute from Jersey City who last was seen alive May 1 in Oak Beach. Gilbert remains missing.

Monday's search will mark the first time that a canvass will occur off the barrier island.

Nassau County police will be contributing about 20 officers to the canvass, said department spokesman Det. Lt. Kevin Smith.

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The search area of the north-south parkway is about 5 miles each way. The Wantagh parkway is about 13 miles in length.

The State Police first publicly mentioned the possibility of looking beyond the barrier island about two weeks ago at a news conference.

The barrier island searches have been redone and expanded repeatedly since December, when a cadaver-sniffing dog and his police handler in the Gilgo Beach area stumbled on the first of four burlap-wrapped skeletons of what turned out to be slain women who worked as prostitutes. Police believe they are the victims of a serial killer.

On March 29, cops found a fifth set of remains east of Gilgo Beach, and a week later, found three more nearby.

On April 11, state and Nassau police found a plastic bag of bones and, separately, a human skull. Last week, searchers found two human teeth that police suspect are from the skull.

And earlier this month, the FBI flew a Black Hawk helicopter over the island to photograph the area. The results of those flyovers are pending.

So far, only the four initially discovered remains have been identified: Maureen Brainard-Barnes, 25, of Norwich, Conn.; Melissa Barthelemy, 24, of the Bronx; Megan Waterman, 22, of Scarborough, Maine; and Amber Lynn Costello, 27, of North Babylon.

Forensic experts are working to identify the other six, police said.

--With Tania Lopez