The old Smurfit-Stone paper mill in Frenchtown is still burning and fire crews are having a hard time fighting it.

The Frenchtown Rural Fire Department was notified that a pile of trash was on fire at the mill site around 6:30 p.m. Sunday. Firefighters tried to douse the flames at the five-story building, but had trouble reaching them safely.

By 8:30 p.m. the fire had spread to a front building on the site. The fire department still isn't sure how much longer they'll be battling the blaze.

The building is in the process of being demolished. The cause of Sunday's fire is still unknown, though a welding torch is suspected to be the cause of a fire that happened at the mill two weeks ago.

Frenchtown firefighter Mel Holtz says there are no toxic chemicals in the building.

The health department was on site last night and continues to monitor the fire.

NBC Montana will keep you updated as more details become available.