Police have been searching for Sonia Varaschin since her blood-stained car was found abandoned in Orangeville. (HANDOUT)

TORONTO - Missing nurse Sonia Varaschin was the victim of foul play, the Ontario Provincial Police said in an announcement Wednesday.

No further details were released, but OPP Const. Jonathan Beckett said the investigation into the 42-year-old's disappearance Sunday from her home in Orangeville, Ont., about an hour north of Toronto.

From evidence forensic officers found in her Spring St. house, Beckett told QMI Agency: "We believe she has met with foul play ... we're still treating this as a missing person investigation."

Police were called when the petite brunette failed to show up for work Monday.

Her bloodied white Toyota Corolla was found parked in an alley.

It has been removed for forensic tests, Beckett said.

As with the search of her home, where blood was also found, he said: "It takes times to process the scene."

Neighbours told reporters they heard screams from Varaschin's house around 3 a.m. Monday, one insisting tires squealed around the same time.

Police were also canvassing Orangeville residents and businesses on the third day, in their search for clues.

"The investigation is continuing," he said.

"We're continuing to follow up on leads," said Beckett, the spokesman for the joint OPP-Orangeville Police case.

Asked about reports of Varaschin having a boyfriend who visited her home, and that she recently quit her job at a Newmarket hospital, he said "we're not commenting on what her situation is, either at present or in the past."

Beckett also declined to provide specifics about evidence found at the home, saying they are key to the investigation.

He would also not comment on any search of her home phone or cellphone records.

"It stands to reason every avenue is being explored."

A press conference is planned for 3 p.m. Wednesday.

Meanwhile, in nearby Bolton, Ont., an Orangeville-marked police cruiser and two unmarked police vehicles were parked outside her parent's home.

An officer who answered the door told a QMI Agency reporter the family had requested privacy and "now was not a good time" to speak with them.

A friend who went to school with Varaschin, and who kept in touch via Facebook as recently as two weeks ago, called her "a super nice gal."

Varaschin is 5-foot-1, 125 pounds, and has brown hair with light streaks.