Suffolk officials yesterday concluded a painstaking, four-day canvass in the Gilgo Beach area that had recovered three more human remains, and the search now moves to Nassau and Jones Beach beginning Monday.

The search through thick, rough terrain in the serial killer investigation will continue, said Suffolk Police Commissioner Richard Dormer, who acknowledged Thursday that something could have been missed this week.

Late last year, Suffolk police found four skeletons wrapped in burlap off an isolated section of Ocean Parkway in Gilgo Beach. All proved to be the remains of young white women who worked as prostitutes; none were Shannan Gilbert, 24, the Jersey City woman police have been looking for.

Suffolk investigators believed the women were murdered by a serial killer and dumped in underbrush between 2007 and September.

"A special warning to women who are engaged in the escort business: They should be very careful in their contacts," Dormer said Thursday.

Another four human remains -- so far unidentified -- were found March 29 and Monday.

At an afternoon news briefing, Dormer Thursday called the search of the 71/2-mile-long area "unprecedented" in the county.

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Starting early Monday, State Police troopers, Nassau officers on horseback and others will begin to crisscross a 4-mile stretch between Tobay Beach Park and the Jones Beach tower.

"After Suffolk County found these four more bodies, it had to be done," said Nassau police spokesman Det. Lt. Kevin Smith.

The primary area of interest is a bramble-thick wildlife sanctuary and the adjacent, undeveloped state land between the parkway and South Oyster Bay, officials said.

Mounted police will traverse trails through the sanctuary for an elevated view, police said. Using the search method developed by Suffolk police this week, officers will mount raised firetruck buckets to move out over thickets. Others will be on foot.

A Nassau County medical examiner official will be on hand to distinguish animal bones from any others that are found. A police helicopter also will be used, Smith said. The search is expected to go at least into a second day.

All eight remains were discovered during searches for Gilbert, who has not been found and was last seen alive in Oak Beach on May 1. Like the remains of the four women initially found in December, Gilbert worked as a prostitute and advertised on the Craigslist website. Like the others, she went missing while visiting clients.

Fifty state troopers will participate next week, as will members of State Park Police, said Trooper Frank Bandiero of the State Police. The agency will also provide several cadaver dogs that participated in a December search over frozen ground that failed to reveal the four remains found recently in Suffolk.