St. Louis, MO  (KTRS)  An investigation is underway after two sisters in their fifties were found dead in their north St. Louis home.

Police say the boyfriend of one the sisters found made the discoveryTuesday morning at a home in the 3100 block of Whittier Street. Haz mat was called in after preliminary tests of air levels in the home indicated the presence of hydrogen cyanide.

Authorities say at least one of the women had been shot. The names of the victims haven’t been released.