The man who police once called a "person of interest" in the case of the disappearance of Lyle and Marie McCann has now been named a suspect in the case.

Police say the investigation is considered to be a suspicious missing person case in which they believe that the disappearance of the couple was a result of foul play. Investigators now say Travis Vader is a suspect in the case.

"It's the positive progress we've made in the investigation, which now validates Mr. Vader as a suspect," said RCMP Sgt. Tim Taniguchi. "In all types of investigations, we get information and it's ongoing information from a number of different sources...this could be from witnesses, through interviews, through statements, through tips," he added.

Lyle and Marie McCann left for B.C. on July 3rd and have not been seen or heard from since.

The McCanns' burned-out motor home was found on July 5th near the Minnow Lake campground approximately 35 kilometres southeast of Edson. On July 16th, their green Hyundai SUV was located deep in the bush about 30 kilometres east of Edson near Carrot Creek.

Vader was arrested in mid-July on charges unrelated to the couple's disappearance. Vader was picked up by officers at a rural residence near Niton Junction.

The couple's son Bret McCann believes police are now one step closer to finding his parents.

"You know we're viewing this as a positive step in the investigation. We're looking at this as bringing us a step closer to finding my parents and a step closer to ending this nightmare," he told CTV News.

Bret's sister, Trudy Holder, made a desperate plea Tuesday aimed directly at the man who police now call a suspect.

"Please step forward and tell me where my mom and dad are and end this nightmare," she said.

Last month, Vader's sister told CTV News last month that she didn't believe her brother is capable of hurting anyone. Bobbi-Jo Vader admitted her brother had been dealing with serious drug problems in recent years, and said she was glad he is in custody getting some help.

Mounties have been questioning locals in Vader's hometown west of Edmonton about the man's actions on one particular day.

Sources in Peers, Alta. say police activity here in recent weeks has focused on a convenience store.

Sources tell CTV News that in the weeks since media first showed in the small town where Vader grew up, RCMP investigators have shown up to the store and have asked about the surveillance cameras inside.

Questions have also been asked about whether Vader purchased a phone card inside the store on July 8th.

Community leaders in St. Albert have also joined forces with the family of the couple by helping raise money for a reward aimed at finding the missing couple.

About $30,000 has already been raised for the fund from an anonymous donation.

The new reward is in addition to the $2,000 reward being offered by Crime Stoppers for tips leading to the whereabouts of the McCanns.

With files from Bill Fortier and David Ewasuk