A week after the post office in downtown Winthrop was destroyed by fire, the U.S. Postal Service has begun making plans to replace the facility.

The interior of the post office was gutted and its metal roof collapsed after a fire started in its attic last Tuesday morning. Its brick walls are still standing, but they will need to be knocked down, said Steve Doherty, a spokesman for the Postal Service.

“They’re going to need to demolish what’s left of the building,” Doherty said. “The plan right now is just to rebuild on the same location. That’s what (the Postal Service is) moving towards.”

Doherty couldn’t offer a timeline for the work.

The post office had operated at 112 Main St. for the last seven years after replacing an older facility that was difficult for handicapped citizens to enter. Firefighters responded to the fire at 8:54 a.m. shortly before it opened for business, but the lobby of the post office was open to members of the public.

After employees noticed smoke coming from a ceiling tile and heard a crackling sound, the building was evacuated, Doherty said last week. No one was injured during the response.

Because it was a federal building, the Bureau of Alcohol, Tobacco, Firearms and Explosives is investigating the cause of the fire.

“At this point, there is no official determination on the cause of the fire, and it still remains under investigation,” said Christopher Arone, a spokesman for the bureau, in an email Monday afternoon.

It may take a while for the investigators to announce any findings, Doherty said, because they want to look for additional evidence when the post office is being demolished.

For the time being, Winthrop residents and businesses that had post office boxes will have to pick up their mail at the Manchester Post Office on 31 Readfield Road, Doherty said. Delivery of mail to Winthrop addresses will continue out of the Augusta Post Office, but items that require a signature and can’t be delivered will be left in the Manchester location.

The Postal Service announced those temporary solutions last Tuesday. A day later, a crew of workers from the U.S. Postal Inspection Service went to Winthrop to remove all mail from the burned out building, but it’s unclear how much of it was salvageable.

Some of the mail seemed to be in fine condition, while other pieces were wet from the water that firefighters had sprayed into the building on Tuesday, said Emily Spera, one of the inspectors.

Now, inspectors have turned over that salvaged mail to the Postal Service. It will be dried out and decisions will be made about what can be sent to customers and what is too damaged to be recovered, Spera said.

In an email, Doherty said that “several tubs and trays” full of mail were recovered and transported to a processing facility in Portland. That mail would be “cleaned and sifted through,” Doherty wrote. “Anything with a legible address or barcode will be delivered. This process will likely take a few days.”

Several Winthrop residents and businesspeople who were at the Manchester Post Office last week said they were worried about various items being destroyed. One woman said she was expecting a state tax refund of about $600. The executive of a printing business said he was waiting for a customer’s payment.

“It sucks,” said Austin Knight, a Winthrop man who was expecting a baseball cap celebrating the New England Patriots’ Super Bowl victory to arrive in the mail and was worried it was lost.

Charles Eichacker — 621-5642

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Twitter: @ceichacker