Caltrain delayed by tunnel fire

SAN FRANCISCO -- Several trains operated by Caltrain were delayed by more than 20 minutes Friday after crews doused a minor fire in a tunnel at 18th Street Friday afternoon, a Caltrain spokeswoman said.

Transit police responded to a report of a fire at 3:30 p.m. in tunnel no. 4, which is one of the four tunnels that take commuters into San Francisco, said Caltrain spokeswoman Jayme Ackemann.

Ackemann said the cause of the fire was still under investigation.

"It's not clear what happened," Ackemann said. "There are homeless encampments in the area, so this may be related to that."

Fire crews cleared the scene by 4:10 p.m.