While searchers aggressively followed up on leads, a Regina Police spokeswoman is hinting time may be running out for a happy ending in the case of Tamra Keepness.

"The likelihood of a happy ending to this becomes more remote," Elizabeth Popowich told reporters about what may be the largest missing person's case in Regina's history.

On Sunday, the search extended to a farm field on the southeast outskirts of the prairie city more than 10 kilometres away from Tamra's central Regina home -- much further than a five-year-old would likely walk on her own. Volunteers walked through the field in a grid, using hockey sticks and ski poles to part the tall grass. A canine unit sniffed along the treeline.

Police wouldn't say why they searched that location, but they have followed up on hundreds of leads.

For example, some aboriginal elders had a vision that Tamra might be found near water. On Saturday, a boat cruised Regina's Wascana Creek.

"Any of that that would help us or even point us in a direction -- we've been following up on all of that," Popowich said.

Eleanor Keepness, the missing girl's aunt, thanked everyone who was helping to locate Tamra.

"I thank everybody that’s helping, putting up the posters, Whoever is helping, I really thank you. The family thanks you. Any help you can give, anything," she said, fighting back sobs.

Tamra, one of six children, was last seen Monday night going to bed. She was discovered missing Tuesday morning.

Dozens of trained volunteers, police officers, canine teams and cadets from an RCMP training academy have been working 16-hour days, from 6 a.m. to 2 a.m.

Tamra's disappearance is still being treated as a missing person case. Police say they have no evidence that the girl was abducted.

But Popowich said investigators are considering the possibility that Tamra was taken by someone cruising a nearby area frequented by prostitutes.

Her family thinks that is a possibility. Her uncle Scott Keepness demanded her safe return, saying: "You know who you are. You have the power to bring her back."

On Friday, Tamra's family sent police to a marshy area near Regina's airport. The couple acted on a a tip from two aboriginal elders. They claimed to have seen visions of the girl in that part of the city. In the end, there was nothing there.

The realization is growing that the search can't be kept up at this level forever, although police say they have many places yet to check. "There are a lot of resources that have been brought to bear on this. We're not at the point yet where a decision has to be made. But it will come," Popowich said.

"If they are going to give up, we are not going to give up," Eleanor Keepness said. "I don't care, we are going to get our own search party together. Our Keepness family will continue the search."

Police say Tamra may be wearing a light blue striped halter top with pink accents, light blue jeans, and pink and white shoes.

Anyone who has seen the girl or has any information about where she might be is asked to contact the Regina Police Service at (306) 777-6500 or call Saskatchewan Crime Stoppers Crime Stoppers at 1-800-222-TIPS (8477).

With a report from CTV's Jill Macyshon