BOISE--A crash on Interstate 84 around noon today backed up traffic for nearly four miles between Boise and Mountain Home

Idaho State Police say a semi-trailer carrying a propane tank tipped over spilling the propane onto the freeway.

At one point all the lanes were closed forcing travelers to spend some time on the side of the road.

Now all the lanes have been reopened.

However, the west bound off ramp leading to the port of entry is still closed.

"On the travel trailer, the individual left his propane tanks turned on and during the crash, the cup was broke which caused the propane to start leaking everywhere, that is what caused the hazmat situation, get fire crews to respond so that we could safely remove the tanks so they wouldn't start an explosion," Cpl. David Neth, Idaho State Police.

Idaho State Police are investigating the crash. Officers on scene say a gust of wind likely pushed the trailer over.