A fourth man has been arrested over the hanging of effigies from the stands during the last Celtic-Rangers game.
The 17-year-old has been held in connection with alleged offensive behaviour, police said
It is understood the arrest relates to two blow-up dolls - one wearing a Rangers scarf - being strung up in the home section at Celtic Park on September 10.
It follows the arrest of two men - aged 22 and 27 - on Thursday over the incident.
All three are expected to appear at Glasgow Sheriff Court on Friday.
A 27-year-old man was arrested earlier in September and has already appeared in court over the incident.
Police are investigating a series of incidents at the match, which Celtic won 5-1.
A 26-year-old man has been arrested over alleged offensive singing and officers are looking into the vandalism of toilets within the away section of Celtic Park.
Images appeared on social media after the match showing toilet doors and roof tiles smashed, and police are appealing for anyone with mobile phone footage of the scene to contact them.
Meanwhile, a man has been arrested over a pitch invasion during the Aberdeen-Rangers match on September 25.
The 23-year-old man been charged with breach of the peace and is expected to appear at Aberdeen Sheriff Court at the end of October.