The State Fire Marshal’s Office announced Friday morning what led up to the deadly propane blast in Farmington that killed one fire fighter and injured others.

They say the underground propane line was severed during the installation of one of four bollards.

The installation of the posts took place six days prior to the September explosion at the Leap Incorporated building.

Investigators say the bollard work was done by Techno Metal Posts of Manchester, Maine.

Although they know what caused the leak, they say the ignition source cannot be determined.

Fire officials says criminal charges are unlikely.

The blast claimed the life of Farmington fire captain Michael Bell.

Six other fire fighters and maintenance supervisor Larry Lord were hurt in the explosion.

Lord remains hospitalized more than four months later.