The services have been disrupted and there is a significant delay in the operations. We are negotiating with the striking motormen and are hopeful of an early resolution of the issues," a Western Railway spokesperson told PTI.
He did not give give details about the number of services cancelled.
Thousands of commuters were stranded at various stations due to the sudden stir.
The Western Line is the busiest of the three suburban lines in the metropolis and carries on an average of over 3.4 million on its 1,250 services on both directions every day.