A Chelsea woman was held without bail following her arraignment on murder and arson charges stemming from the death of 20-year-old Crystal Lynn Blanchard in a fire on Christmas Eve, Suffolk County District Attorney Daniel F. Conley said.

MELISSA PFEIFFER (D.O.B. 1/12/84) and her boyfriend lived at 265 Spruce St. in an apartment below that of Blanchard and her boyfriend, Assistant District Attorney Mark Lee said during this afternoon’s proceedings in Chelsea District Court.

“On the evening of Dec. 24, the defendant and her boyfriend became involved in an argument,” Lee said. “Generally speaking, it was over money. The argument ended at about 10:00 or 10:30 p.m. and the boyfriend left the building.”

Pfeiffer’s boyfriend returned to the building at about 11:00 and saw Pfeiffer leaving the building, Lee said.

A short time later, the prosecutor said, a car occupied by four people drove by the Spruce Street scene. The occupants, who were lost and in the area by pure coincidence, saw the flames and called 911. That call brought Chelsea firefighters and police racing to the scene.

Blanchard and her boyfriend were trapped by smoke and flames on the building’s second floor. The boyfriend suffered serious burns before finally jumping from a window and further injuring himself.

“Miss Blanchard was unable to get out of the building,” Lee said. “She subsequently died of her injuries.”

Two separate witnesses have reported hearing Pfeiffer admit that she had set her boyfriend’s clothes on fire, Lee said. While a comprehensive report by fire investigators has not yet been completed, Lee said, those statements corroborate “strong indications” at the scene that the fire had been deliberately set.

The investigation into the fatal fire is ongoing, Conley said. It is led by State Police homicide detectives assigned to the Suffolk DA’s office, who have jurisdiction over all death investigations in Chelsea, Revere, and Winthrop. They are aided in this case by Chelsea Police detectives, the Chelsea Fire Department, and State troopers assigned to the State Fire Marshal’s office.