Plans to build an arena for the Sixers in Center City have fallen through, and the team plans to stay in South Philadelphia, sources close to the negotiations say.

It is a head-spin development from the fight the 76ers have lodged over the last two years when it sought to build a new arena in Chinatown and close to the city’s center, and as it went to battle with Comcast,

The team, whose ownership group is led by investor Josh Harris, said it had formed a 50-50 joint venture with Comcast to replace its arena in the South Philadelphia stadium district by 2031. Comcast will also take a minority stake in the team and work together on the WNBA bid, the parties said in a joint statement Monday.