Vancouver Mayor Gregor Robertson says police, outreach workers and volunteers will be out on the streets making sure homeless people know where the shelters are. (CBC)

The mayor of Vancouver and police are trying to find options for compelling homeless people to move off the streets in sub-zero temperatures following the burning death of a woman who had lit a fire in a makeshift shelter to keep warm.

Mayor Gregor Robertson said he had a discussion about the matter with Vancouver police Chief Jim Chu on Friday.

"There is an issue of civil rights there that we have to grapple with, and that is the challenge right now, particularly with people who choose to remain or are convinced that they belong outside," Robertson said.

The 47-year-old woman's body was found burning in a makeshift shelter built around a shopping cart at Davie and Hornby streets around 4:30 a.m. PT Friday, police said.

A 47-year-old homeless woman was found burned to death after a fire in her shopping cart early Friday morning. (CBC)

The woman, known as Tracey, came to Vancouver last month after living on the streets in the Abbotsford area for a number of years, Const. Jana McGuinness said Friday.

"She was checked by our officers on at least three occasions overnight and offered shelter, which she declined," McGuinness said.

"The officer that checked her last had a conversation with her, offered her a small comfort in the form of a cigarette, and lent her his lighter when she asked to borrow it to light a candle."

Tracey's activities after that were unknown. Investigators are asking anyone who may have had contact with her in the area between 12:30 a.m. and 4:30 a.m. to call police.

McGuinness said police cannot force people off the streets no matter how cold the weather, except in very limited circumstances.

Vancouver police Const. Jana McGuinness says police cannot force people off the streets except in limited circumstances, such as under provisions of the Mental Health Act. (CBC)

"If there is a legal authority that we can act under that we can compel someone to go, say for example the Mental Health Act, where we believe they are a danger to themselves or the situation or they are not competent to make that decision then, yes, we can," she said.

"We cannot if we believe that that person is fine and is making an independent decision."

Meanwhile, Robertson said police, outreach workers and volunteers will be out on the streets making sure homeless people know where the shelters are.

Two emergency shelters in Vancouver have been opened since temperatures dipped below zero this week. Two more shelters are to open in the next few days.

"We are opening shelter space for people with carts and pets, who might otherwise avoid a shelter, and we are going to keep working hard throughout this tough weather to protect people from harm," Robertson said.