Southbound Caltrain service is running 10-20 minutes behind schedule this morning due to a malfunctioning signal in San Francisco, Caltrain spokeswoman Christine Dunn said.

The problem signal is located near the 22nd Street station. Maintenance crews are working to repair the signal.

In addition to the delays to southbound trains, northbound train No. 225 is 12 minutes behind schedule, Dunn said.