A large fire has broken out at ‘The Flying Monkey’ theater in Plymouth, New Hampshire, according to officials and witnesses. A concert was taking place at the time. The fire began just after 9 p.m. on Saturday when the band Foreigners Journey, with special guest Constantine Maroulis, was holding a concert at the theater on Main Street. An estimated 500 people were inside the building when the fire broke out, according to first responders. Most of them were evacuated but it’s unclear if anyone is still inside. Footage from the scene shows parts of the theater engulfed in flames, with the fire s…