LIMESTONE (AP) – Three people who had run out of oil and were using a wood stove and a kitchen stove as heating sources died Tuesday in Maine’s deadliest fire in six years, authorities said.

The Maine Fire Marshal’s Office said the early morning fire started in the kitchen area of the home, near where a wood stove was situated. Investigators did not immediately determine the cause of the fire.

Fire investigators identified the victims as 35-year-old Kelley Holmquist, her 10-year-old son, Trevor Holmquist, and a friend, 37-year-old Alex McDougall.

Authorities said oil was to have been delivered to the home hours after the fire broke out.

An Aroostook Sheriff Department deputy, Sgt. Larry Goff, discovered the fire at 12:53 a.m. while on patrol and attempted to enter the home but was forced back by intense smoke and heat, authorities said.

The two-story building, which was originally a three-unit apartment house but had only one unit currently occupied, collapsed as firefighters were battling the fire.

Excavating equipment was needed to assist in the recovery of the bodies.

Authorities said Holmquist’s other son, who is 12, was staying with his father, John Holmquist, in Presque Isle on Monday night.

Fire marshals were aided by firefighters from Limestone and Loring in the search for victims.

Authorities said Holmquist was found in the kitchen area at about 10:20 a.m., and McDougall was found in the living room at 12:05 p.m, while the boy’s body was found in the remains of his bedroom an hour later.

Investigators believe the two adults may have been awakened by the fire and were attempting to escape or reach the boy’s bedroom.

The bodies were taken to a local funeral home.

State officials said the last time three people died in a fire in Maine was in January 2000, in Unity.