SALISBURY - Police are cracking down on scofflaws in town, conducting late-night searches for cars residing in Massachusetts but registered in New Hampshire.

Already, they have found a staggering number of vehicles registered in the Granite State but parked overnight in Salisbury.

"The midnight shift has already found more than 100 New Hampshire registered cars here, and we haven't even canvased the whole town yet," said Salisbury police Chief David L'Esperance. "This is a big problem. It's a question of fairness, really."

Police in border towns from Salisbury to Salem, N.H., and points west have long watched for scofflaws, who typically try to fool the registry to save hundreds of dollars on excise taxes and car insurance, which is cheaper and not always required in New Hampshire. As recently as October, officials from both states have vowed to work together to renew their efforts to target the so-called "rate-jumpers."

While scofflaws could potentially face auto insurance fraud charges, in Salisbury, police are threatening fines; though, the violations could ultimately lead to revocation of driving priveleges in the stae.

According to L'Esperance, the problem with Massachusetts car owners who illegally register vehicles in the Granite State is three-fold: the state registry of motor vehicles loses money; Salisbury loses valuable excise tax revenue that supports town services; and state mandated vehicle insurance is often missing.

"I don't think you have to have car insurance in New Hampshire unless you've had a car accident," L'Esperance said. "In Massachusetts you do, and there's a fine attached if drivers are found without it if they're stopped or get into an accident here."

The fine can run anywhere from $100 to $1,000, L'Esperance said, depending on the number of times owners are found in violation of registration requirements or the severity of the specific charge. Initially, the charge may be driving an unregistered vehicle, he said, but it can escalate to more serious violations.

Owners can appeal for a judge's ruling, L'Esperance said, but if the out-of-state registration is again found to be illegal, owners can lose their right to drive in Massachusetts.

Police don't take on the job of checking for improperly registered cars during the summer because there are so many out of state people who vacation here. Now that winter is upon them, however, police are out logging out of state plates as they patrol town roads each night. In addition, L'Esperance said, officers are getting a little help from residents.

"We've been getting a lot of calls and e-mails from people who are expressing their displeasure about Salisbury residents who register their cars over the border in New Hampshire," he said. "It's actually been very interesting."

Once the entire town has been surveyed, L'Esperance said, police will send warnings to vehicle owners with suspect New Hampshire plates. If owners don't get the message, formal complaints will be issued. L'Esperance said based on the evidence, the clerk of courts will then determine if the New Hampshire registration is improper. If so, a fine would be levied.

Precautions are taken in neighboring Seabrook to prevent out-of-state residents from taking advantage of the system, said Seabrook Town Clerk Bonnie Fowler. A New Hampshire driver's license isn't required to register a car in Seabrook, she said, but proof of residency must be established, and a light or phone bill doesn't qualify.

"If they come and say they've bought land in Seabrook, we ask to see proper papers from the bank," Fowler said. "If they're renting, we want to see proof from the property owner ... or a lease for their apartment. ... You can't live in a post office box. We don't take a post office box address in Seabrook as a proof of residency for registering a car here."

Fowler's office sends out monthly notices for annual registration renewals, and precautions are again taken to ensure those renewing Seabrook registrations still reside within the community. Renewal notices returned by the post office are noted in the computer, she said, and proof of residency must again be presented before renewals are granted.

There are even rules for car registration for those who own property in Seabrook but live elsewhere for all or part of the year, Fowler said.

"The registered car has to be housed in Seabrook," Fowler said. "If people go to Florida for the winter, their car is supposed to stay here."

And, just like L'Esperance, Fowler's office gets calls from local residents who report when they believe the rules are being broken.

L'Esperance said some people still have the notion that registering vehicles in New Hampshire costs less than doing so in Massachusetts. A Seabrook resident himself, L'Esperance doesn't believe that's true.

"If you actually compare the money it costs, there isn't really much of a difference," he said.