Good news from the Party Patrol: Based on the number of arrests so far, the county-wide crackdown apparently is discouraging underage drinking.

Forty people were arrested throughout King County on a variety of charges last weekend, the debut of the annual effort by police agencies to keep teenagers away from alcohol during celebrations of the end of the school year.

The Party Patrol will continue this weekend and “seems to be working. Arrests are down,” said John Urquhart, a spokesman for the King County Sheriff Department, which coordinates the multi-agency campaign.

Sheriff deputies and officers from city police departments, including Black Diamond’s, are working with state Liquor Control Board agents to break up parties with underage drinking. Authorities are also targeting stores to prevent sales of liquor to minors.

In the southeast King County area, no illegal parties were found last weekend. But among 27 businesses that were checked to see if they’d sell alcohol to someone clearly not 21 years old, two did. One was in Black Diamond, and the other was in an unincorporated area of the county. Offending clerks at the stores were cited and released, Urquhart said.

Elsewhere countywide, 28 of the 40 arrests were for being a minor in possession of alcohol. Of the rest, two were for driving offenses (one drunk, one reckless), two were for drug possession, two were for obstructing police officers, and one was for furnishing alcohol to minors. In addition, three people were arrested after outstanding misdemeanor arrest warrants against them were discovered, officials reported.

People younger than 18 who are found drinking will be arrested, then released to their parents or booked into youth detention. Offenders between 18 and 21, as well as parents or other adults providing the premise for an illegal party, will receive a misdemeanor citation or will be taken to jail.

Urquhart said this time of year is when parties in celebration of graduation, end of school and beginning of summer “are at their peak.”