PITTSBURGH — Commuters in Pittsburgh who use its light rail system are feeling the after-effects of a freight train derailment.

Seven rail cars from a freight train derailed Sunday near Station Square, sending shipping containers tumbling down a hillside onto light rail tracks.

With Station Square out of service, light rail users who live in the southern suburbs are being forced to switch to shuttle buses to complete the trip into the downtown area Monday. Commuters from the north have to switch to buses if they want to get to the city’s South Shore.

Transit officials say it should take up to three days to clear Station Square and assess the damage. The agency expects full service to be restored in days, not weeks.