OLD ORCHARD BEACH — Old Orchard Beach police conducted a sting targeting the sale of alcohol to underage customers this week, and of the 21 businesses they checked, four sold alcohol to a minor, they said.

The violations, according to police, occurred at Friendly’s Market, Olde Town Country Store, Barefoot Boy Restaurant and Jumpin’ Jake’s. In each case the server or clerk asked for and checked identification and then still sold the alcohol even though the person wasn’t old enough to buy it legally, police said.

Administrative violation notices were issued to each of the four.

The 17 other businesses checked did not serve the minor posing as a customer. The department used two reserve officers who are 20 to conduct the compliance check.

The police statement, issued by Deputy Chief Keith Babin, said the compliance checks would continue through the summer.