Four Goodwill buses caught on fire in North Haven on Monday.
Now, fire officials are warning all drivers to watch where they are parking or else their car could suddenly go up in flames.
Goodwill officials believe that hot mulch caused the fire.
They say it's possible when temperatures heat up like they did on Monday.
Gusty winds caused the flames to fan the fire. Surveillance video caught the fire spreading to the vans.
The damage totaled more than $200,000.
"We never figured this, these vehicles, we've been doing this for years, nothing's ever happened," said Keith Lavalette, Goodwill Vice President of Programs.
Lavalette said hot mulch, which was put don just one week ago, could be to blame.
"When they backed the vehicles up, we think the exhaust or the hot muffler started the fire," said Lavalette.
Fire officials explained how hot mulch, fresh or not, can ignite under certain conditions.
"Anytime you put a heat source next to something that burns, you stand the opportunity or likelihood that there could be something that ignites. Given the fact that the mulch is pretty dry because of the lack of ran, that could lead to it," said Deputy Chief Scott Martus of the North Haven Fire Department.
Martus says no matter the size of the car, mulch isn't the only combustible. Tall grass is also a problem at this time of year and a car's distance to it is a huge factor.
"You'll see that a lot if you go to different shopping centers and what not if you pull into a spot and see a pile of mulch sitting there, smoking, that's because someone threw a cigarette on it or parked too close to it," said Martus.
There was also a concern over fiberglass, which is highly flammable, moving to the gas tank.
The cause of the fire is still being investigated by the fire marshal.
Since it was so hot, extra firefighters were called in to help. Instead of working the typical 30 minutes before a break, they were stopping at 15 minutes to hydrate and cool down.
The vans shuttled Goodwill employees to various stores across the state. The organization says they'll double up with the other working vans to get by.
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