CNN  — 

At least four of the eight people killed in Monday morning’s boat dock fire in northeastern Alabama were children ranging in age from 7 to 16, a coroner said Tuesday.

The other four who died at Jackson County Park Marina at Guntersville Lake are presumed to be adults, county Coroner John Jordan said. The victims’ names have not been released, and dental records are being used to identify the remains, he said.

The preliminary investigation is focused on “one boat in particular,” Scottsboro Fire Chief Gene Necklaus told reporters Tuesday. The boat was being examined off site by state and federal investigators.

Identification of remains will depend on the forensic work required, including the use of dental records and possibly even DNA, according to Necklaus. “That could take up to six months unfortunately,” he said, adding that names would be released by the State Fire Marshal’s Office.

The fire, starting not long after midnight, tore through numerous boats that were docked at the lake. Some of the boats were occupied, and the flames forced several people to jump into the water to escape.

Some of the roughly 35 destroyed vessels were houseboats where people lived full-time. Seven people swam to safety or were rescued, and were taken to a hospital for treatment, officials said.

Investigators are trying to determine what caused the fire.

This photo provided by Mandy Durham shows Monday morning's fire.

Paul Smith, director of the Jackson County Emergency Management, said work crews on Tuesday were recovering debris and containing and collecting fuel that spilled. Water samples were being taken.

“They don’t expect any human impact or environmental impact,” he said.

Four boats that drifted away and sank about 250 feet from the dock have to be removed, Smith said.

There are simultaneous investigations being conducted by the US Coast Guard and National Transportation Safety Board as well as the State Fire Marshal and federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

Thought officials were “cautiously confident” about the number of fatalities, dive teams remained on site in case other remains were found.

‘People … were jumping into the water’

Firefighters arrived around 12:40 a.m. local time Monday to a chaotic scene, Necklaus told HLN.

“People … were jumping into the water, either off the back of their boats or retreating to the end of the dock just trying to avoid the fire before they had to,” Necklaus said Tuesday. “Several people would pile up in a boat, it appears, and then try to push away from the dock.

“But boats were burning, floating off, bumping into each other and setting other boats on fire just as fast as you can imagine.”

The fire’s location – on a covered dock that extended well out into the lake – made it difficult for firefighters to access, Necklaus told reporters a day earlier.

“Those boats burn at such a fast rate, and in that environment with the (dock’s) wood structure and the full roof, that fire spread so quick, so much quicker than you can imagine.”

The dock that burned is the one that extends farthest to the right in this file photo, according to Chief Deputy Rocky Harnen of the Jackson County Sheriff's Department.

Authorities said late Monday afternoon that it appears everyone is accounted for, although that will not be finalized until all the boats have been removed from the water and inspected.

Shane O’Neal, owner of Southern Marine Towing & Salvage, told CNN affiliate WAFF that his team lifted one vessel Monday that had four bodies inside.

The seven people taken to a hospital were treated and quickly released, the fire department said. Some had minor injuries or minor hypothermia from the cold water.

CNN’s Eric Levenson and Jamiel Lynch contributed to this report.