The National Police confirmed on Thursday that officers in Timika, Papua, had dispersed a mass gathering in the city after spotting a Morning Star flag that was raised in the celebratory event commemorating the Free Papua Movement’s 50th anniversary.

National spokesman Insp. Gen. Saud Usman Nasution said that the celebration started off harmless, with traditional singing and dancing by the local women. However, the joy turned sour when police saw the outlawed flag being waved.

“The local deputy police chief was forced to break up the mass of people there,” he told The Jakarta Post on Thursday.

He said that officers on guard at the location confiscated the flag. Three people were reportedly arrested over the incident.

Saud said that the incident in Timika was one of only a few sightings of the flag on the day of the OPM anniversary.

“There was one in Wamena at 6 a.m. and another one in Puncak Jaya, Jayawijaya. We took the flags down,” he said.