Investigators in Burnaby, B.C., say they are now treating 13-year-old Marrisa Shen's death as a homicide, but do not yet have a motive or suspect.

"Right now there is no evidence to indicate to investigate whether it was targeted or random," said Integrated Homicide Investigation Team Cpl. Meghan Foster.

"Public safety concerns remain unknown."

Shen was last seen leaving her home near Central Park in Burnaby on July 18, around 6 p.m. PT. She was reported missing around 11:30 p.m., and her body was found in the southeast corner of Central Park around 1:10 a.m. the next day.

Police are sharing a short video of Shen entering an apartment building in the area that day, prior to her last known whereabouts, wearing what they believe is the same clothing she had on when her body was discovered.

Investigators hope the visual aid will help anyone who may have seen Shen that evening come forward with any information.

Foster said they're still in the crucial stages of gathering evidence and do not have a suspect, motive or exact cause of death. But they don't believe Shen's death is linked to any other criminal acts in the region.

"To assume that it's related to any act of violence in the Lower Mainland at this time would be premature," she said.

"Initially, I would say it's an isolated incident, but it's still too early in the investigating to confirm anything like that."

The Integrated Homicide Investigation Team is investigating the death of Marrisa Shen, 13. (Tina Lovgreen/CBC)

Police are not saying what led them to Shen's body less than three hours after she was reported missing.

They continue to extensively canvass the 86-hectare Central Park, the majority of which is covered by wooded trails.

"The park is large, and what we're trying to do is create a systematic search pattern to canvass the entire park, so we don't miss anything," said Foster.

Anyone with information is asked to contact IHIT at 1-877-551-4448, by email at ihitinfo@rcmp-grc.gc.ca, or, if they wish to remain anonymous, Crime Stoppers by phone at 1-800-222-8477.