A rash of car break-ins in Fair Haven has spread to neighboring towns, local departments said Monday.

In addition to break-ins reported in Red Bank and Fair Haven, Rumson, Shrewsbury and Little Silver have reported unlocked vehicles entered over the last few days, and police are putting residents on high alert.

Rumson police received five reports of unlocked vehicles — all on the west side of town near the Fair Haven border — that were entered and electronics and personal items stolen sometime between Sunday night and Monday morning, Detective Chris Isherwood said.

“Same M.O. as Red Bank, Fair Haven: unlocked vehicles,” he said. “We definitely have somebody out there.”

There may be more, Isherwood said.

“By five o’clock today you might get 10 more people calling in,” he said. “Obviously our radar gets heightened and you kind of wait for the other shoe to drop.”

Shrewsbury police have also seen the same problem as Fair Haven, which, for the last two weeks, had unlocked cars broken into and various items stolen. Reports of more break-ins in Fair Haven this weekend have not yet been confirmed by police.

Shrewsbury Police Chief John Wilson said for the last month the northwest section of the borough has seen a number of break-ins. He didn’t have an exact figure ready Monday afternoon.

And in Little Silver, Detective Sergeant Daniel Shaffery said two unlocked cars were entered on Judith Road between Thursday night and Friday morning and change was taken.

It appears the incidents are connected, he said, but at this point there are a number of possibilities.

“You can assume that it is (the same suspect) but it could be two or three crews going out,” he said. “When this happens you go to the usual suspects, but there’s nothing solid on it yet.”

About a year or two ago, Little Silver saw a spate of break-ins, but an increased police presence and the help of aware residents tamped down the crime, he said. He hopes that’ll be the case this time, too.

“We just want our residents to realize you have to lock your doors,” Shaffery said.

The departments, in addition to increasing patrols and conducting investigations, are working together to catch the suspect or suspects and are alerting residents to keep their doors locked and remove valuables from their vehicles.

Rumson intends to send out a reverse 9-1-1 call to residents, Isherwood said. Shrewsbury is taking steps to keep the area safe, Wilson said.

“We’re increasing patrols. They have an order to check side streets more often,” he said. “We are doing a number of things.”