Northumbria Police statement: "A flare was thrown from the section containing Manchester City fans into a section of Newcastle United fans, no one was injured and it was quickly extinguished.
"A second flare was set off in the section containing Manchester City fans.
"Officers at the scene carried out extensive enquiries, including checking CCTV and speaking with available witnesses.
"However, the person or people responsible are yet to be identified.
"We take incidents such as this extremely seriously and enquiries are still ongoing. Officers continue to work with colleagues at Greater Manchester Police."
Manchester City Fixtures
Saturday December 22 15:00 Manchester City v Reading
Wednesday December 26 15:00 Sunderland v Manchester City
Saturday December 29 15:00 Norwich City v Manchester City
Tuesday January 1 2013 15:00 Manchester City v Stoke City
Sunday January 13 2013 16:00 Arsenal v Manchester City
Saturday January 19 2013 15:00 Manchester City v Fulham
Tuesday January 29 2013 19:45 QPR v Manchester City