Ontario Provincial Police have released a surveillence video from a park in Orangeville to try to identify two people they say could be witnesses in the unsolved murder of a local woman.

Sonia Varaschin was reported missing four years ago on Aug. 30, 2010 after she failed to show up for work. Her body was found days later in a wooded area on Grange Side Road in Caledon.

Police say it's believed the 42-year-old nurse was murdered in her home on Spring Street, and have said her car and home were stained with blood.

They've released surveillance video of a gazebo in Alexandra Park behind Orangeville's town hall - in an area close to where police say Varaschin's vehicle was left in the early morning hours of the day she disappeared.

The video, which can be viewed on the Ontario Provincial Police's YouTube page, depicts two people in a gazebo prior to them walking away at around 6 a.m. that day.

"They could have seen Sonya's vehicle at that location in behind the town hall in Orangeville or could have seen the vehicle dropped off." said OPP Sergeant Peter Leon

Police say the two are potential witnesses and not suspects in the case and are asking anyone who recognizes them to contact the force immediately so investigators can identify and speak with them.

A reward of $50,000 continues to be offered for information leading to the arrest and conviction of the person or persons responsible for Varaschin's murder.

The case drew national attention as investigators revealed the culprit likely left Varaschin's home covered in a significant amount of blood and used her car to move her body to the wooded area where it was found.

"Our investigators are as committed to finding Sonia Varaschin's killer today as we were when it began in 2010," said OPP Det. Insp. Shawn Glassford.

"We are determined to bring justice to Sonia and her family," he said.

"No tip is too small or insignificant in fact it could be the missing piece of the puzzle that we need to solve this case."

With files from the Canadian Press.