"Urgent" pre-planned construction work by MTA construction crews caused severe service disruptions on the 7 train Monday morning, transit officials said.

Straphangers accustomed to riding the 7 train for their morning commute started their day on a partially suspended line.

Pre-planned weekend construction work, which was expected to wrap up by 5 a.m Monday., took longer than anticipated, leading to an extension of a service suspension in both directions between Queensboro Plaza and 34 St-Hudson Yards, the agency said.

New York City Transit President Richard Davey said conduits in the Steinway Tube, which connects the 7 train between Manhattan and Queens, were installed improperly, and a test train hit the conduits.

"So inches turned into hours for many of our customers here," Davey said.

Service on the 7 train resumed as scheduled, with severe delays, at around 9:30 a.m. Monday, the MTA said.