Police in Barrie have laid dozens of additional charges against a father and son at the centre of an investigation that forced roughly 60 residents out of their homes last month.

William Feldhoff, 75, and his son, Donald Feldhoff, 54, face 44 charges in relation to improvised explosive devices and chemicals discovered by police in their Barrie home.

The senior Feldhoff also faces 39 charges for firearm offences.

The father and son were charged in the 1978 murder of Michael Traynor.

Feldhoff was charged with first-degree murder after his arrest on July 11. His father was charged with being an accessory after the fact the following day.

A search warrant obtained July 12 led police to discover numerous explosives and chemicals at the home the father and son shared.

Police found 26 illegal firearms, more than 11,000 rounds of ammuniation and over 80 improvised explosives devices.