BOISE -- An offramp from Interstate 84 remains shut down after a semi truck caught fire Wednesday morning.

The fire began at about 6:45 a.m. on the Vista Avenue offramp from westbound I-84. The exit is completely blocked.

The semi driver was not hurt in the fire, dispatchers said.

The blaze appears to have begun inside the trailer of the semi, which was hauling tires, and quickly expanded into a large fireball. The cause of the fire is unknown.

Boise Fire responded to the scene with two engines and a firetruck. Fire crews cut a hole in the side of the trailer to more easily douse the flames inside.

The fire has been extinguished, but the large charred hole is visible in the middle of the trailer.

Boise Police tweeted the offramp will remain closed for "an undetermined amount of time." Drivers should plan to take another route and use caution around emergency vehicles.

Check back for updates.