BALTIMORE, Md. (AP) — A fire that killed two first responders and engulfed multiple rowhouses in northwest Baltimore last year has been ruled accidental, according to an investigation released Friday by the Baltimore City Fire Department.

The cause of the Oct. 19, 2023, fire that killed Baltimore firefighters Dillon Rinaldo, 26, and Rodney Pitts III, 31, remains unknown. However, officials ruled out an electrical system failure and improperly disposed smoking materials, like cigarettes, according to the Bureau of Alcohol, Tobacco and Firearms. The blaze began in the rear of a first floor on Linden Heights Avenue, officials said.

An investigation by Maryland Occupational Safety and Health found no legal or regulatory violations, the Baltimore Sun reported.

“The loss of our colleagues in the Linden Heights fire is a profound tragedy that deeply affects our entire department and the community,” Baltimore City Fire Chief James Wallace said in a Friday statement. “Our firefighters put their lives on the line every day, and it is heartbreaking when such sacrifice results in loss.”