PITTSBURG (KPIX 5) – Nearly three weeks after electrical issues were discovered, BART service resumed between the Pittsburg/Bay Point and North Concord stations Tuesday morning.

A mysterious power surge disabled dozens of train cars last month, forcing riders to take shuttle buses and shuttle trains between the two stations.

Since the problem was discovered, that part of the line has been tested by technicians as they try to figure out what triggered the power surge. BART has still not determined what is causing the electrical issue.

Service between the two stations may be interrupted again if BART decides there’s still some issues. But that decision won’t be made until after the Tuesday morning commute.