Two people from Calais are at University of Vermont Medical Center in Burlington with life-threatening injuries after a fire at their house.

Vermont State Police say Elizabeth Busch, 77, and William Klein, 80, were home on Max Gray Road when the fire started shortly before 8:30 a.m. Saturday. The house took extensive damage from flames, heat and smoke.

VSP is investigating the cause and origin of the fire. Based on what they’ve learned so far, however, they say the fire does not appear to have been intentionally set.