BALTIMORE (WJZ)—Last month, an early morning house fire killed four children and their grandmother who tried to save them. Now fire investigators and arson detectives have determined the cause.

They found that the fire was caused by combustible materials placed too close to a furnace.

Fire officials say the fire started just before 3 a.m. Oct. 11 in the basement of their Northeast Baltimore  home, located in the 5600 block of Denwood Avenue.

The flames then traveling all the up until they shot out of the roof.

All five victims were found in the back bedroom: 7-year-old Tykia Manley, 4-year-old Darryl Stewart, his sister K’niyah Scott, 1-year-old James Holden Jr. and their 55-year-old grandmother Nancy Worrell.

A funeral was held for the victims at Mount Pleasant Church and Ministries.

The fire department reminds citizens to keep ordinary combustible materials at least three feet away from heat producing appliances.  Gasoline and other flammable materials should never be stored inside your home.

If you are in need of a working smoke alarm, please call 311. Within two hours firefighters will arrive at your residence to install a smoke alarm on each level of your home.