After four days of searching, there was still no sign Friday of a small plane that vanished in B.C.'s Okanagan region with four men aboard.

Thirteen aircraft and at least 60 people were searching the area for the missing Piper PA24, which hasn't been heard from since leaving Penticton for Victoria on Tuesday.

But Canadian Forces Capt. Scott Cursley, the man in charge of the search, says that he's confident the plane will be found soon.

"It's better than the proverbial needle in the haystack because of the professionalism of the crews. They know what they're looking for.They're trained to look in the hay for the needle," Cursley told CTV News.

He said searchers are looking for any scrap of evidence of the plane.

"It could be a swath of trees that have been knocked down, it could be a disturbed rock."

A $10,000 reward is being offered by a friend hoping to motivate others to take up the search.

The exact reason for the flight to Victoria hasn't been established yet, but some media outlets have reported that the plane was connected to the drug trade.

RCMP Cpl. Dan Moskaluk said that police are aware of those reports, but are focusing on assisting search crews.

"The priority at this time is locating this aircraft," he said. "We're not in a position at this time to speculate as to the exact nature of this flight."

Craig Wolf, a friend of missing pilot Rama Tello, told CTV News that he's disappointed with speculation about the plane.

"It hurts the family, hurts the friends, children, husbands, wives. It's just improper in a time like this," Wolf said.

With a report from CTV British Columbia's Penny Daflos