Materials have been sent to a laboratory for testing and examination, and the cause is believed to be accidental.
But investigators will not be able to determine how the fire started until the remaining witnesses are interviewed, authorities said.
“This is not going to be an easy one or a fast one,” DeHaven said of the investigation.
The last fatal fire in Hagerstown was at a home on Calvert Terrace in January 2009, Wolfe said.
The building at 334 Summit Ave. is a six-unit apartment building owned by The Turret, LLC. Only two units were occupied, but the tenants of a basement apartment were not home at the time of the fire, Wolfe said.
People drove slowly by the scene on Thursday morning to look at the damage. Much of the building’s roof had been burned away.
A day earlier, firefighters recovered the body of a woman, and rushed the girl and the two men to Meritus Medical Center east of Hagerstown.
On Thursday morning, charred debris, including a child’s shoe, was stacked in small piles at the rear of the building.
A burned chair and other household items littered the front yard. Yellow police tape was strung around the building, and orange signs that said “condemned” were posted on the front and rear exits.
The couple who was not home at the time of the fire returned Thursday morning to salvage some of their belongings.
Danielle Runner and her boyfriend, Diego Saenz, were escorted inside by fire officials.
“We were just grateful we weren’t in there,” Runner said. “I was shocked. I could have been sleeping. I’m a hard sleeper. Anything could have happened.”
She said she accompanied Saenz on a truck-driving job to New Jersey. They left their apartment at 5 a.m.
Wednesday and were on their way home on Interstate 81 about 45 minutes from Hagerstown when a friend called to break the news, Runner said.
She said she lost numerous belongings, including birth certificates and irreplaceable photographs.
The couple said they didn’t have renter’s insurance.
“I would say 60 percent of everything will be salvageable,” Saenz said. “Most of my stuff is in storage, so I didn’t have a lot of things here.”
Saenz, who said he recently retired from theU.S. Marine Corps, hoped his military records weren’t destroyed.
Runner said the Red Cross of Washington County was putting them up in a hotel for a few days until they could find another place to stay.
Angie Burns, who owns the building at 334 Summit Ave. with her husband, Jim Burns, said the building had two apartments on each of the three floors.
Tenants were scheduled to move into two of the other units in May, she said.