'Absolutely terrible': Victorian mother still missing after days of searching

The desperate search for a mother who failed to return home from a run in regional Victoria has entered its third day.

Samantha Murphy, 51, was last seen leaving her home on Eureka Street in Ballarat East to go for a run in the Canadian State Forest, about 7am on Sunday.

Police have told media they do not suspect anything suspicious has happened, but are concerned for Murphy's welfare after weather conditions reached stifling temperatures.

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Murphy had her phone with her when she left her house, which last pinged telecommunications towers in the Buninyong area, about 11 kilometres south of her home.

Police have expanded the search after focusing efforts near the Buninyong Golf Club, with a large number of community members joining the search.

Murphy's husband Mick told 9News he was staying at home during the search to try and keep his mind busy while he waited for an update.

Friend Chris Stapleton described the mother as a lovely person and said her disappearance was out of character.

"She's a lovely, quiet lady I always thought," he said.

"It's just absolutely terrible. We've come out just to help out in any little way."

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Volunteer Donne Crouch said the area being searched dense and expansive.

"There's mine shafts, that's the biggest concern is that the mine shafts out there aren't very noticeable in some areas," she said.

The search will pause again today from 8pm before resuming tomorrow.

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Acting Inspector Lisa McDougall said Murphy was an experienced runner but family and police were concerned due to the heat, which reached 36 degrees in Ballarat on Sunday.

"Obviously (her family) are very upset and concerned because this is very out of character for Sam," McDougall said.

"We're going to look into all of the possibilities of where she might have gone so far."

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Murphy is described as Caucasian, about 173cm tall with a slim build and shoulder-length blonde hair.