A father and his four-year-old daughter who were the subjects of an extensive search in a Milton, Ont., conservation area were found dead late Sunday, police say.

The pair were discovered at the base of a rocky cliff with "significant trauma" that would be "consistent with a fall," Halton Regional Police spokesperson Const. Ryan Anderson said at a Monday morning news conference.

The effort to find the two began around 7:30 p.m. ET Sunday, after police received word that they had not returned from an afternoon hike at Rattlesnake Point Conservation Area, which is about 60 kilometres west of downtown Toronto.

Their bodies were located just after 11 p.m.

"It's certainly not the outcome we were looking for and it's the outcome we were dreading," Anderson said.

The child has since been identified by her mother and stepfather as Keira Kagan.

"She's a precious little girl," Jennifer Kagan said of her daughter. "Keira was absolutely a doll, an absolute angel, adored by absolutely everyone."

Watch: Jennifer Kagan talks about her daughter, Keira.

Jennifer Kagan speaks about her daughter Keira, who was found dead at the base of a cliff at a Milton Ont. conservation area. 1:16

Keira lived with her mother and stepfather, Philip Viater, in Thornhill, north of Toronto. She was visiting her father for the weekend, Kagan said.

The father has been identified by Kagan and Viater as Robin Brown.

"It feels like a nightmare," Kagan said. "I pinch myself thinking I'm going to wake up from this and you don't. It's an unbelievable loss."

Robin Brown, right, and his daughter, Keira, were reported missing Sunday evening after police received word they had not returned from an afternoon hike at Rattlesnake Point Conservation Area. (Submitted by Jennifer Kagan)

The force's homicide unit has taken control of the investigation, even though it is not currently considered a homicide probe "at this time," Anderson said. The unit investigates any case involving the death of a child under five years old.

Viater said their family is still processing the tragic news, especially since Keira was supposed to return to them on Monday.

"We're going through cycles. Cycles of shock, disbelief, pure grieving, anger," he said.

A mix of rain and snow would have made for dangerous hiking conditions, Const. Steve Elms said in an earlier interview at the scene overnight.

"The terrain is pretty rugged," he said. "The area is very forested and can be slippery."

The conservation area includes several cliff-side trails, and hikers have died there in the past.

Their bodies were removed from the conservation area overnight with the help of firefighters.

Anderson said that the police search included Halton's Search Incident Response Team, as well as the K-9 and tactical rescue units. It was hindered by the wintry weather, he said.

Anyone who was in the conservation area between 2 p.m. and 11 p.m. yesterday and may have valuable information for investigators is asked to contact Halton police.