EDMONTON -- Police in Edmonton have released surveillance video pictures of two people who they say may be able to help them in the case of a toddler who was found dead outside a church.

The grainy images appear to show a man and a woman, both wearing ball caps, pushing a stroller as they enter a store.

But investigators say they still don't know the identity of the boy, estimated to be about 20 months old, whose body was found by a passerby on Friday.

And they now say they believe the boy was left in the area on Tuesday morning, days before his body was discovered.

The mystery has left many people in Edmonton asking a perplexing question.

Where are the parents?

"Wouldn't the parents notice he was gone and wonder, where was he?" asked Donna Miller, who passed through Good Shepherd Anglican Church's parking lot Saturday on the way to catch a bus at the transit terminal next door.

It was the same thing many of the people coming and going from a bake sale and lunch inside the church wondered as they passed a small collection of flowers and a teddy bear that have been left at the scene.

Investigators have issued a public plea, retweeted by Premier Rachel Notley, for information on the child's identity.

They've also shown clothing that the boy was wearing in the hope it might prompt someone to come forward with information.

Spokeswoman Cheryl Sheppard said Edmonton police are still piecing together events between Tuesday, when she said investigators think the boy was left in the area, and Friday's discovery.

Sheppard said the images of the two people was recorded Monday. Police believe they may have information critical to the investigation.

The church is in a busy area. Besides the nearby transit terminal, there's a fire station right beside it. There's also a public library and strip mall next door and a recreation centre not far away. Condominiums and a seniors lodge are also close.

"My heart just really aches to think of this thing happening," said Marryman Porter, who attended Saturday's bake sale in the church.

One woman, after laying flowers next to the teddy bear on Saturday, hugged another women she'd arrived with.

Tears were visible in her eyes. They didn't stay long and the pair climbed back into an SUV that, like many vehicles in the city this weekend, was flying Edmonton Oilers flags as the NHL team hoped to clinch Game 6 of the NHL's Western Conference quarter final Saturday night.

Homicide detectives are working on the case and an autopsy is scheduled for Monday.

At a news conference Friday night, Staff Sgt. Duane Hunter said "someone out there" is missing the child.

The clothing police showed included a blue snowsuit bearing the logos "U.S. Polo Assn" and "USPA Polo Assn."

There was also a blue T-shirt with a Batman logo on it, and a black and grey sneaker with lime green and blue detailing.

"Something like this happening so close to where you live, it's not good," said Bob Murphy, who lives in the nearby condominium building.

"What happened or why, I don't know."