CHARLTON — As firefighters scrambled to find water in an area without hydrants, a rapidly spreading blaze tore through a former mill Thursday night and destroyed nearly everything inside, including more than a dozen rare vintage cars.

“This is my worst nightmare,” said Gary Cove of Wilbraham, who lost seven personal vehicles and seven rare vintage cars he had repaired or was in the process of repairing or servicing for clients across the United States. He said a 1933 Rolls Royce was “burned to a crisp.”

“I’ve been doing this for 38 years. This stuff is irreplaceable. I don’t know what to do; this is my whole world. I’m 56 years old,” he said.

Cove estimated the loss was at least $2 million, but said he has insurance. He said he managed to save the most expensive car, a 1957 Mercedes 300SL valued at $800,000.

Cove’s son was inside the historic wooden Charlton Woolen Mill when the fire erupted at about 9 p.m., and he escaped without injury. Six firefighters were treated at a hospital for heat exhaustion.

The five-alarm fire at the old mill-turned-warehouse raged for at least two hours, and firefighters continued to put water on the charred debris through Friday afternoon, dousing still-smoldering areas.

Firefighters from far away as Brookfield provided aid, with trucks and firefighters from 20 different municipalities assisting overnight. They were relieved Friday by firefighters from 20 other towns or cities in the region.

At least seven tanker trucks shuttled water in from Glen Echo Lake, officials said. The tankers filled two square retaining pools erected on the parking lot of the mill, and fire trucks siphoned water from those pools to supply their hoses. They also siphoned water from a shallow pond nearby.

“For a mill of this size, [getting enough] water right up front is a problem,” said Sheri Bemis, Oxford fire chief.

Ten businesses were housed at the former mill on City Depot Road, and authorities are taking a close look at one in particular, after reports that a worker may have accidentally set fire to a cloth with sparks from a saw he used.

“We can’t confirm anything at this point, but that is something that is being looked at closely,” Bemis said.

Witnesses said the blaze initially appeared small enough to pose no problem, but then suddenly grew and consumed the building. High flames cracked in the night sky and the intense heat could be felt more than 100 yards away.

“By 10 o’clock, it was really on fire,” said Rebecca Taylor, who lives across the street from the mill. “It looked like there was a tornado inside.’’ She said she heard explosions that appeared to come from propane tanks inside the complex.

The mill sits near protected wetlands, and fire officials along with the Department of Environmental Protection worked to prevent any contamination as they focused on containing a 275-gallon tank of heating oil in the building.

As a precaution against spillage and to contain any unknown contaminants that may have been in the flow-off of water used to douse the blaze, officials laid a boom around the nearby pond.

“Who knows what has soaked into the wood from the multiple uses over the years,” Bemis said.

There was no spillage detected from the heating oil tank, but the Federal Emergency Management Agency and the DEP took water and air samples and the results were expected back next week, said Frederick Swensen, vice chairman of Charlton’s Board of Selectmen.

Charlton has historically drawn its water from wells, but a public water supply is about to be in service, Swensen said. That would allow the town to add hydrants.

“We are in the process of developing a public water supply, particularly in this part of town, and that’s under construction now,’’ Swensen said. “We’re turning water on as we speak.”

Cove said his clients have included such celebrities as designer Tommy Hilfiger. In addition to the 1957 Mercedes, he said, he was able to save a 1964 Shelby Cobra valued at $700,000, and an Alfa Romeo worth $165,000 that was parked outside the building.

“I had photos of my wedding in there on my desk, and just life’s stuff,” Cove said. “I loved and worked in that place; it was like my little museum.”