CAMDEN — Traffic in downtown Camden slowed to a crawl along Route 1 at 4 p.m. today as regional fire departments responded to the Camden Post Office, with reports of smoke in the historic building.

But the afternoon’s tempo resumed it normal pace after it was determined that the cause of the smoke was traced to a light ballast.

“The ballast burned out, and created some smoke and odor in the post office,” said Fire Chief Chris Farley.

The fluorescent bulb was behind the service area, where staff sorts the mail and puts it in the mailboxes. The Camden Post Office was built in 1913, and is on the National Register of Historic Places.

Staff evacuated the building and called 911. Camden firefighters responded, as did Rockport, Lincolnville and Hope, per mutual aid agreement.

The excitement was over in 20 minutes and everyone went back to business.