The explosion and police investigation led to major service changes on a number of subway lines.
UPDATE, 9:52 p.m., per mta.info:
A, C and E trains are now stopping again 42nd Street-Port Authority Bus Terminal, but customers will be forced to leave the station to transfer to the 1, 2, 3, N, Q, R, W and 7 trains, and the 42nd Street shuttle, as the passageway connecting 42nd Street-Port Authority Bus Terminal and Times Square-42nd Street is currently closed due to a police investigation. No additional fare will be charged.
Services resumed at Times Square-42nd Street on the 1, 2, 3, N, Q, R, W and 7 trains, and on the 42nd Street shuttle, shortly before noon Monday.
Service had been disrupted on all of those lines earlier in the morning in the aftermath of the explosion.