San Francisco Muni riders may have to do without NextMuni for several weeks.

As reported earlier on Thursday by SFBay, the NextBus system called NextMuni in The City, has been experiencing technical difficulties since Wednesday on predicting accurate arrival times of Muni buses and trains.

Officials at the SFMTA issued an advisory Thursday morning warning passengers that NextMuni was going through intermittent outages and had disabled predictions inside the Muni Metro and a few other lines.

SFMTA spokesperson Paul Rose said in an update on Thursday that a technical issue is causing NextMuni to display inaccurate predictions and that the transit agency is “working aggressively” to resolve.

Rose said it could take a matter of weeks to restore all of the missing Muni predictions. He said by next week, the transit agency will have a better timeframe on when the predictions will get restored.

The transit agency has been going through an upgrade with the NextMuni system. The system uses AT&T’s wireless cellphone network to transmit the data to the NextMuni screens.

Data had been transmitting through NextMuni using a 2G network, which AT&T had deactivated because the technology is now outdated.

SFMTA officials said the deactivation happened sooner than expected so some Muni vehicles may not show up on NextMuni because they simply do not have the upgraded communications and monitoring system yet.

Rose said about 70 percent of Muni vehicles, including trains, have the older new communications system in place yet inside the vehicle. Newer Muni vehicles that have arrived in 2013 and later have newer systems which do not experience this problem.