BOSTON -- Four Massachusetts police departments announced renewed efforts to crack down on illegal alcohol purchases by minors with the Cops in Shops program.

“This program sends a clear message to minors -- if you’re too young to buy, don’t even try. We are confident that this program will allow us to be pro-active in discouraging minors’ attempts to purchase alcohol illegally,” said Attleboro Police Chief Richard Pierce.

The program puts plain-clothed, undercover officers into liquor stores in participating communities posing as customers and store employees, Pierce said. Stores agreeing to work with law enforcement have signs on the door and inside the store clearly stating undercover officers may be posing as store employees, said Pierce.

Cops in Shops has been an ongoing program, but with the holidays approaching police are trying to make a renewed effort to crack down on underage drinking, Pierce said.

"We're trying to be vigilant, because we remember the tragedies, and a lot have been alcohol related," said Pierce.

The program also allows for undercover officers to be posted outside the stores to try and stop adults from buying alcohol and providing it to minors, Pierce said.

"We are very enthusiastic about this program,” said Chris Gasbarro a program organizer and owner of Seekonk’s Fine Wine & Spirits and North Attleboro’s Capodanno’s Package Store. “We welcome the opportunity to partner with law enforcement officials to combat the issues of underage drinking and the illegal procurement of alcohol."

The towns of Attleboro, North Attleboro, Mansfield and Norton are all participating in the program and will be sharing the funding, Pierce said.

In the past, Cops in Shops has been paid for through a state grant, but police worked hard to secure donations from local retailers and from the departments themselves because they weren't sure grant funding would continue, said Pierce. So far they've been able to collect about $9,300 from retailers, he said.

Police like the program because it's very flexible -- officers could be in the liquor stores at any time -- which acts as a deterrent, said Pierce.

Anyone under age 21 who attempts to purchase alcohol is subject to a fine up to $300 and a 180 day suspension of their driver's license, according to Massachusetts state law. Adults who purchase and provide alcohol to minors face up to a $2,000 fine and/or a jail term of up to one year.

Police are thanking local retailers for their support, said Pierce. The program is anticipated to continue indefinitely.

"[The store owners] are sending the message that illegal procurement of alcohol beverages and underage drinking will not be tolerated in our communities," said Pierce.