As the search expands for a Winnipeg teenager who's been missing for five days, Cooper Nemeth's family is beginning to fear the worst.

"I'm not naïve to think that we may possibly find a dead kid," Nemeth's aunt Laresa Sayles told CTV Winnipeg on Thursday. "But we're keeping hope."

The search for the 17-year-old has expanded, with the Winnipeg Police Service looking for any sign of Nemeth outside of the city’s limits.

Nemeth was last seen early Sunday morning after leaving a party. He has not checked in with family or friends since.

His father has said the disappearance is very unusual, as Nemeth typically texts his family about his whereabouts.

On Thursday, police peered through the windows of empty houses under construction, checked ditches and looked in other areas that could be dangerous for untrained civilians to search.

Earlier in the week, police focused their search to Winnipeg's downtown, responding to a tip that Nemeth had been spotted in the area appearing confused.

Police have also appealed to the public for help finding two witnesses, known as Derek and Brittany, who may have been with Nemeth in the early hours of Feb. 14.

"We just hope he's safe and we can find him soon and bring him home to his family," said Ange Arbuckle, who works with Nemeth's mom.

Anyone with information is asked to call Winnipeg police at 204-986-6250.

With a report from CTV Winnipeg