AMHERST, Mass. (AP) — Investigators have not been able to determine the cause of a fire at an Amherst apartment complex last year that killed a University of Massachusetts student.

The Jan. 21, 2013 blaze took the life of 21-year-old James Hoffman, a business major from Stoughton. An autopsy determined he died of smoke inhalation.

The state Fire Marshal's office says the fire at Rolling Green apartments started directly in front of the closet in Hoffman's second-floor bedroom, but investigators were not able to identify any known heat source. Electrical experts ruled out the apartment's electrical system as a possible cause.

More than 30 people were displaced by the fire.