Police released new images of a dark-coloured vehicle Monday which was spotted close to where Victoria Stafford went missing last month -- among the first new bits of evidence in the case released in weeks.

The make and the model of the station wagon haven't been identified yet, but police hope the images will spur additional witnesses to come forward.

"The driver of the vehicle is believed to potentially be a valuable witness to this incident and the Police would like to speak with this person," police said in a release on Monday afternoon.

According to surveillance images, the vehicle was seen driving on the same street where Victoria and her alleged captor were also spotted.

Release of the images had been delayed as police attempted to improve their grainy quality.

The eight-year-old girl was last seen walking away from her elementary school on April 8 with an unidentified woman.

Investigators describe the woman as being 19 to 25 years old, at least 5'1" tall and weighing about 125 pounds. She is believed to wear her long dark hair in a ponytail.

Officers in Victoria's hometown of Woodstock continue to canvas door-to-door in search of clues about the girl's whereabouts.

Meanwhile, the Ontario Provincial Police scoured a landfill site east of the town of Salford.

Officers are also asking local farmers tending their fields to be "extra vigilant" to look for anything unusual or suspicious.