Suffolk County Police received the initial call at 6:13 a.m. after the crash involving two cars and the truck at Route 25 and Main Avenue in Lake Grove.
The truck carrying nearly 4,000 gallons of home heating oil flipped over, causing a large fire that engulfed all three vehicles.
Everyone inside the vehicles was able to get out safely.
No significant injuries have been reported.
The fire was so big it knocked out power lines - causing outages in the area.
Route 25 between Wood Road and Hawkins Road is expected to be closed all day for the investigation and cleanup.
Motorists are advised to avoid the area.
* More Long Island news
* Send us a news tip
* Download the abc7NY app for breaking news alerts