A three-alarm fire broke out Monday morning at the Eugene O’Neill Theatre on Broadway, which shows "The Book of Mormon," causing substantial damage to the fourth floor of the building, according to the FDNY. Performances were canceled through Wednesday, producers said.

Firefighters responded to the blaze after 10 a.m. Monday at 230 West 49th St. Fire officials said 63 units responded to the incident, with nearly 200 fire and emergency medical personnel on the scene.

According to FDNY Assistant Chief David Simms, the fire started in an electrical room between the fourth and fifth floors of the building, where lighting equipment and chandeliers are also stored.

“This was a deep-seated fire involving a lot of electrical equipment. It was very difficult to get to. There were a lot of catwalks and rigging in the theater,” Simms said at a news conference.

He said that after the fire was extinguished, firefighters discovered more fire between the fifth floor and the roof of the building.

Ambassador Theater Group, which owns the theater, said in a statement that everyone working inside has been safely removed from the building. The group also said the team behind the production will assess the damage and announce any additional changes to scheduled performances as soon as possible.

Performances were canceled for Tuesday and Wednesday, according to a spokesperson for the production. Ticket holders will be notified at their point of purchase about exchanges or refunds, the spokesperson said.

The FDNY said one firefighter suffered minor injuries and was transported to a local hospital.

The theater first opened in 1925. FDNY officials said the building would be out of service pending the necessary repairs.

The city Department of Buildings is also investigating the incident.

According to the Museum of Broadway, "The Book of Mormon" has been on Broadway for 15 years, performing out of the Eugene O’Neill Theatre. The museum said that’s the 10th-longest-running show in Broadway history.

This story has been updated with additional information.