Church fires of all sizes, including Monday's massive blaze at Notre Dame Cathedral in Paris, are generally "really very hard to fight," according to CBS News Radio correspondent Bill Rehkopf, a volunteer firefighter for 30 years.

"I'm not there, [but] just looking it, it's as if the dye was probably cast by the time firefighters arrived," Rehkopf told CBSN.

The fire was high up on the roof, which Rehkopf said presented a logistical challenge. Also, the cathedral sits on an island in the middle of the River Seine, which may have made it difficult for firefighters to get their apparatus into position.

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If there was an opportunity to get in and rescue some of the cathedral's priceless works of art, firefighters would most certainly do it, Rehkopf said. But large statues and huge religious artifacts would almost certainly be impossible to remove. And firefighters would have to be concerned about the structural integrity of the stone walls, which may have been weakened by the intense heat.

"You could try to go inside and do something with it, but with all of the flammable material inside a church and with those old timbers that build up and comprise the trusses of the roof, they go up like tinder, and you don't want to put your people in the road of anything that might collapse," he said. "I'm just afraid the losses at this point will be tragic."

Rehkopf said the fire presented a worst-case scenario for firefighters.

"The entire roof structure between where the spire stood and the bell towers has collapsed into the cathedral itself," he said. "Now you've got the fire and you've got the timbers and you've got the wreckage down into the nave of the building, and that's where the artifacts and the works of art are that people are so justifiable concerned about."

Paris police said the cause of the blaze at the 12th-century cathedral was unknown, but the fire was "potentially linked" to the renovation work being carried out at the site, French media quoted the Paris fire brigade saying.

"The investigators will look very, very closely at that once they get things in control and are able to interview the people who were there and around the scene," Rehkopf said.

He added that there were a number of possible causes for the fire -- from an electrical problem to something as simple as a tossed cigarette.

"Whether it's somebody working on a roof or somebody outside of their house, casually throwing a cigarette into a potted plant next to vinyl siding, which is like liquid gasoline when it catches fire, from the smallest of sparks -- and we've seen this with the wildfires out west -- you can see such devastation," he said. "And that's why firefighters are always preaching prevention and awareness about where you're doing things."

Another factor was the heavy wind Rehkopf said was pushing toward the front of the cathedral.

"Instead of burning toward the back where [firefighters] might have been able to contain [the fire] and try to keep the front of the building secure, the wind pushed that fire along the roof line up to the iconic bell towers," he said.

Rehkopf said the fire will never be forgotten by those who fought it.

"Firefighters really had their hands full when they got here today, and certainly this is one that they'll go back and talk about for the rest of their careers," he said.