San Francisco’s cable cars were taken out of service due to poor air quality conditions, the San Francisco Municipal Transportation Agency announced Thursday afternoon.

The agency announced in a tweet that “all cable cars will be pulling back into the cable car barn.”

Routes that will be serviced by bus shuttles for the remainder of the day are the Powell, Powell-Hyde, Powell-Mason and California lines, according to the agency.

It is unclear whether cable car service will resume on Friday.

lwaxmann@sfexaminer.com