BARRIE, Ont. -- Residents of a Barrie neighbourhood evacuated as experts deal with explosive devices found during a homicide investigation could be out of their homes for up to 24 hours, police said Thursday.

Const. Angela Butler said about 25 homes were evacuated as a precaution Thursday evening after police determined there were explosive devices and chemicals in the residence.

"It's different various types of explosive devices and volatile chemicals, some of which they (investigators) are aware of what they are, and some, right now, they're not aware," Butler said Thursday night.

Butler could not say what quantity of explosives were found in the home but said identifying the devices and chemicals was a "very slow process."

Butler said she did not know how many people were involved in the evacuation.

"We have confirmed that there are explosive devices and chemicals within that home," Butler said. "We need to take all precautionary measures with the surrounding area."

Butler said most of the evacuees will be staying with family or friends in the area but police were prepared help those with nowhere to go find accommodation.

The explosives were discovered Thursday afternoon as officers with the Barrie and provincial police forces executed a search warrant in a cold case investigation.

A father and son wanted in the 1978 slaying of Michael Traynor were arrested in the home, Butler said.

Donald Feldhoff, 54, is charged with first-degree murder and his father, William Feldhoff, 75, is charged with being an accessory after the fact.

Traynor's family reported him missing on Sept. 18, 1978, when the Barrie resident was 26.

His body was found with obvious signs of trauma in a bush area in Springwater Township, north of Barrie, a few weeks later.