Contributed Photo by Chattanooga Fire Department / Authorities released this photo of the East Lake fire site on Fourth Avenue.

Chattanooga Police and Fire Department investigators are investigating after human remains were found Tuesday at the site of a fire in East Lake.

The fire during the early hours of Sunday at a commercial structure at 2603 Fourth Avenue left one Chattanooga firefighter injured.

(READ MORE: Fires damage three Chattanooga-area homes in one day)

"A firefighter was taken to the hospital after the front façade of the building collapsed on them on the sidewalk, striking him down with debris," said Chattanooga Fire Department Public Information Officer Lindsey Rogers in a news release. He was treated for minor injuries at a hospital and released.

The building, which was engulfed in flames when firefighters arrived, was tackled from the ground and air, according to the department.

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Body found at fire site on Fourth Avenue in East Lake

Once the fire was out, the structure was demolished by Chattanooga Public Works, Rogers said.

(READ MORE: Thursday morning fire destroys Birchwood home, cause under investigation)

"A thorough search was made of the abandoned, collapsed structure as it was dismantled by Public Works to search for any possible victims, and nothing was found at the time," Rogers said.

Tuesday morning, however, "someone was sifting through the rubble and located human remains," Rogers said. "They notified 911 and CFD and CPD responded."

The remains were taken to the Medical Examiner's Office.

(READ MORE: Chattanooga man charged with arson in weekend apartment fire)

The Chattanooga Fire Department is investigating the cause of the fire and is working with the Chattanooga Police Department. Police officials say it is too early in the investigation to determine if there was any foul play.

— Compiled by La Shawn Pagán