ANCHORAGE — It began as a birthday party that drew local snowmobile racers, construction workers and other longtime Alaskans last Saturday night. It turned into a brawl with members of Sarah Palin’s family in the center of it, according to witnesses at the party.

The police are still investigating, and the Palin family is not commenting. But the episode is already adding some more atmospheric notes to the background noise surrounding Mrs. Palin, the former Republican vice-presidential candidate and the former governor of Alaska.

Guests said the event began as a birthday party for twin brothers, Matt and Marc McKenna, the latter a well-known snowmobile racer. Most of the party was outside with dancing and a live band. But then things appeared to get out of hand.

According to a statement from the Anchorage Police Department, officers responded to “a report of a verbal and physical altercation taking place between multiple subjects outside of a residence located on the 900 block of Harbor Circle.”