A large fire at the Winthrop Post Office has closed Main Street.

Centralmaine.com reports the fire was fully involved when crews arrived just before 9 a.m. There are, so far, no reports of any injuries. Departments from neighboring towns were called in to help fight the fire.

Investigators from the State Fire Marshal's office have been called in to help determine what caused the blaze.

We'll update this story as more details become available.