A fire spread to four buildings in Sanford on the same side of Island Avenue where it started, then jumped the street to ignite two others on Thursday afternoon. The five-alarm fire destroyed six buildings and sent four people to the hospital.

SANFORD — A fast-moving fire damaged or destroyed six buildings in the heart of Sanford on Thursday afternoon, sending at least four people to the hospital.

Witnesses said they smelled smoke long before seeing flames in a pile of trash on the back porch of one of the buildings, according to the state Fire Marshal’s Office. The flames spread to four buildings on one side of Island Avenue before jumping across the street and damaging two others, officials said.

“Eyewitnesses told us the fire started outside on a back porch (at 33 Island Ave.),” State Fire Marshal Joe Thomas said. “Some people said they could smell smoke for an hour prior to seeing the fire, which would lead us to believe that it was a smoldering fire. That would suggest it could have been started by a discarded cigarette.”

A team of four fire marshals was expected to spend the night sifting through rubble in the burned out neighborhood and interviewing witnesses before trying to pinpoint the fire’s cause on Friday, Thomas said. Two of the buildings at 33 Island Ave. and 35 Island Ave. were expected to be torn down overnight because they pose a safety hazard.

Four people were transported to local hospitals, including one with a cardiac-related condition. Fire Chief Steven Benotti said one person suffered smoke inhalation and two experienced anxiety. He did not have further information about their conditions.