GREENFIELD, Mass. — Authorities say a fire in Greenfield home last month that killed a longtime Massachusetts State Police employee and three members of his family was caused by smoking.

State Fire Marshal Peter Ostroskey and local officials said Thursday that there were no working smoke alarms in the home and blamed the Sept. 25 blaze on “the improper disposal of smoking materials.”

Killed in the fire were Brian Tower, a longtime state police radio maintenance technician; his wife, Florenda Tower; her son, 28-year-old Raymond Wood; and Wood’s son, 5-year-old William Paul Clark.

Brian Tower had worked for the state police since 1988.

Investigators found that the fire originated in the first-floor bedroom of the single-family home and residents in the second-floor bedroom were trapped by flames.