Firefighters work to put out a fire at the Winthrop post office on Tuesday.

Firefighters from nine area departments battle a big fire at the Winthrop post office on Main Street on Tuesday.

A ladder truck helps firefighters battle the blaze Tuesday at the Winthrop post office.

Firefighters pour water on the Winthrop post office Tuesday morning following reports of a fully involved structure fire.

Firefighters work on scene on Tuesday at Winthrop post office, where fire ripped through the building.

This aerial photo shows the fire damage on Tuesday at the Winthrop post office.

Firefighters work on scene on Tuesday at the post office in Winthrop.

Firefighters work on scene on Tuesday at the post office in Winthrop.

Firefighters work on scene on Tuesday at the post office in Winthrop, where firefighters from nine towns responded to help fight the blaze.

Firefighters work on scene on Tuesday at Winthrop post office.