Passengers on the BNSF, SouthWest Service and Heritage Corridor lines faced significant delays Wednesday morning due to the partial derailment of a SouthWest Service train on the south side of Union Station late Tuesday evening.

Inbound SouthWest Service Train 842 was arriving at the station at about 10:50 p.m. Tuesday when the third, fourth, and fifth cars of the eight-car train derailed. The derailed cars remained upright, and the other five cars and the locomotive remained on the tracks. There were three passengers on the train at the time; there were no injuries. The cause of the derailment is not known at this time.

Metra Alert SWS - Train #818 Arriving Chicago at 9:43 AM - 20 to 25 Minute Delay, Late Arrival of Equipment - Earlier Chicago Union Station, Derailment

— Metra SWS (@metraSWS) November 29, 2017

Crews were still working to remove the train from the scene early Wednesday. Once that is done, repairs will have to be made to several switches that were damaged in the incident. Those switches control a number of routes to the South Concourse platforms, and until they are fixed, all Metra and Amtrak trains will be restricted to a smaller number of tracks, according to Metra, which will likely result in congestion and delays of up to 30 minutes for BNSF and SWS customers and up to 15 minutes for Heritage Corridor customers.

Metra said it is likely that the evening rush period also will be impacted.