Police and explosives experts combed through hidden bunkers, detonated homemade devices and analyzed unidentified chemicals on Friday as they sifted through a Barrie home belonging to suspects in a three-decade-old murder case.

The extensive investigation in this central Ontario city prolonged an evacuation order that has kept 57 local residents out of their homes for the past 24 hours.

Police put the order into effect on Thursday, hours after announcing arrests in a murder investigation dating back to 1978.

Donald Feldhoff, 54, has been charged with first-degree murder in connection with the death of 26-year-old Michael Traynor. His 75-year-old father, William, has been charged as an accessory after the fact.

Provincial Police Det. Insp. Martin Graham said the case broke the day before when Donald Feldhoff turned himself in at a local station.

The subsequent arrest of William Feldhoff, he said, triggered the search of the house where the father and son had lived for decades.

The cache of explosives, chemicals and firearms unearthed there is being handled separately from the murder investigation, he said.

"There's no indication that any evidence inside the residence is linked to the 1978 murder of Michael Traynor," Graham said at a news conference.

The police probe into the Feldhoff residence proceeded slowly as experts picked their way through a thicket of suspicious devices.

Barrie police Staff Sgt. Norm Meech said at least five explosive devices were found outside the home, adding exposed wires were also visible throughout the scene. Several containers of unidentified chemicals were also found toward the back of the home, he said.

Meech said investigators also stumbled on a bunker that ran at least 4.5 metres long and more than two metres deep. A second, smaller bunker is believed to be concealed under the back deck, he said.

'Safety is paramount'

Meech said it's too early to speculate when the order will be lifted. He said the evacuation of 22 nearby homes was a necessary safety precaution given the potential danger of the investigation.

"There are wires around. that's why we have to proceed so slowly," he said. "We understand we are inconveniencing the neighbourhood, but public safety is paramount. We will take our time and we will ensure there's no danger at this residence before we allow neighbours back in."

Police began removing some of the most pressing threats on Friday afternoon, sending plumes of smoke into the air as they disabled two of the homemade explosives.

Meech said many risks remain even when the explosives have been neutralized.

"We have to now deal with unknown chemicals in various containers inside the residence," he said. "After our explosive disposal unit deems it's safe, then we have to begin our criminal investigation into the firearms as well as the making of these explosive devices."

Meech said police anticipate laying further charges in the coming days.

The arrest of the Feldhoffs marked the culmination of an investigation that began when Traynor, who was working as a local plumber's apprentice went missing in the fall of 1978.

Traynor's family reported him missing on Sept. 18, six days after he was seen having a night out with friends.

Police said his body was found weeks later in a bush area in Springwater Township, north of Barrie. Local media reports from that year said he was found with his hands tied behind his back and gunshot wounds to his chest.