Muni Metro service was slowed down by mechanical problems Monday morning, a San Francisco Municipal Railway spokesman said.

The problems began at about 10 a.m., causing delays to light-rail vehicles traveling through the subway system, Muni spokesman Paul Rose said.

“Traffic is still moving, but slowly,” Rose said.

Maintenance crews are working to resolve the issues, Rose said.

He was unsure where the mechanical problems occurred or how long it would take to make repairs.