7 On Your Side Investigates exclusive: BMWs mysteriously bursting into flames

NEW YORK -- BMW is recognized as one of the most reputable car manufacturers in the world, with cars known for reliable engineering and safety.

But in a joint investigation with ABC News, 7 On Your Side Investigates has discovered dozens of cases of parked BMWs bursting into flames. Clues to the cause often go up in smoke, making the fires a growing mystery.

In March 2016 in Orange County, New York, an intense fire ignited in the engine of a BMW that had been parked for hours. The cause, according to investigators, was undetermined.

"A little peculiar," Mamaroneck Fire Chief Tracey Schmaling said. "This car is on fire after sitting numerous days."

Then, in May 2016 in Westchester County, New York, a BMW that had not been driven for days was gutted by fire.

"It was very intense when we pulled up," Schmaling said.

The fire was so intense that it melted plastic fencing and destroyed any clues into what turned the cold engine into an inferno.

"Now we're finding out that more and more of these cars are catching fire for no reason," Schmaling said.

We found dozens of reports of BMWs across several makes and models catching fire after being parked for hours, even days.

Just weeks ago, Sarah and Oscar Day's 2011 BMW, parked for eight hours, suddenly burst into flames in the driveway of their upstate New York home.

"I have no idea," Oscar Day said. "It started in the fuse box. That's where I'd seen it start. Other than that, I couldn't guess."

Along with ABC News Chief Investigative Correspondent Brian Ross, we spent weeks looking into these mysterious BMW car fires. Through fire department data, owner reports and interviews, we've documented 42 cases nationwide of BMW fires involving various makes and models that were not subject to any open, prior fire-related recalls.

And in all 42 cases, the cars were parked.

"Car fires are pretty uncommon," said Sean Kane of Safety Research and Strategies. "But the number of those in which the car is actually off and sitting for a long time are very few. You don't see that as often."

That makes these 42 cases stand out, and it continues to happen, according to a Connecticut BMW owner who found it happened to him three weeks ago.

"It can affect people's lives," Ranbir Gujral said. "What happened if I had this car parked in my garage in a private house? My house would have gone down."

In response to our joint investigation, BMW stated, "With 4.9 million BMW vehicles on U.S. Roads, fire incidents involving BMWs are very rare." The company says they've "investigated and in some cases inspected the vehicles identified by ABC News...and have not seen any pattern related to quality or component failure."

There have been no reported injuries related to these fires, although the millions in property damages mount.

"I'd like them to admit to it, and then make it right," Oscar Day said. "That's all I want."

BMW said that car fires can occur because of "a wide variety of external reasons like poor maintenance, after-market changes and even rodent nest."

ABC News sent its findings to the National Highway Traffic Safety Administration, and while NHTSA said it has found no evidence pointing to a safety defect at this point, the agency is asking for BMW owners who have experienced this issue to reach out to them directly.