State Police homicide detectives assigned to Suffolk County District Attorney Daniel F. Conley’s office and Chelsea Police detectives tonight arrested a Spruce Street woman in connection with the death of 20-year-old Crystal Lynn Blanchard in a Christmas Eve house fire.

MELISSA PFEIFFER (D.O.B. 1/12/84) is expected to face arraignment tomorrow in Chelsea District Court on charges of murder and arson. Pfeiffer was taken into custody this evening at Chelsea Police headquarters.

The charges arise out of Blanchard’s death and injuries to a 33-year-old male after Pfeiffer allegedly set a fire inside her residence at 295 Spruce St. at about 11:00 p.m. on Dec. 24. That residence was a five-unit apartment building; Pfeiffer lived on the ground floor and the victims lived on the second floor.

Pfeiffer was charged amid an ongoing investigation by the Suffolk County State Police Detective Unit, who have jurisdiction over all death investigations in Chelsea, along with the Chelsea Police Department, the Chelsea Fire Department, and State troopers assigned to the State Fire Marshal’s office.

Authorities will not release investigative details tonight. Prosecutors expect to provide a factual account of their case at Pfeiffer’s arraignment tomorrow.