Police are hoping this man might shed light on how two little girls died in a hot car on Saturday.
Darcey-Helen, 2, and Chloe-Ann, 1, died inside a black station wagon parked across the front yard of their family home in Logan, south of Brisbane.
Their mother, Kerri-Ann Conley, 27, has been charged with their murders, as well as possession of dangerous drugs and possession of drug utensils.
Police this afternoon issued a statement saying they were appealing for help identifying a potential witness as part of their investigation into the girls' deaths.
"Investigations have shown that a man wearing a high-visibility shirt walked in a southerly direction along Logan Reserve Road, towards Muchow Road, around 1.15pm that day," they said.
Police are appealing for public assistance to help identify a witness, as part of the homicide investigation into the deaths of two young girls at Waterford West on Saturday afternoon, November 23. https://t.co/jYCJQKUM4B pic.twitter.com/tP6xrBF1ql
— Queensland Police (@QldPolice) November 28, 2019
"Detectives would like to speak with this man as he is a potential witness. He is not considered a suspect."
The man is caucasian in appearance and was wearing a high-vis shirt, shorts, work boots, a white hat, and was carrying a black backpack at the time.
Earlier this week the girls' father called for a full public inquiry into their deaths, saying he wanted "the truth" to be exposed.
"I want a full public inquiry into the deaths of my girls," he said.
"I want those responsible for the inaction that led to my kids being exposed to the situation that they were in to be held accountable.
"I want to expose the truth. The community has a right to know."
It came as Queensland Premier Annastacia Palaszczuk revealed the family was known to the Department of Child Safety.
Ms Conley is the first person to be charged under the Queensland's expanded definition of murder, which includes reckless indifference to human life.
She did not appear in court when her case was mentioned on Monday.
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Gina McKenzie, who said she was the last person to see the girls about 8.30pm on Friday, claimed there had been previous complaints to authorities about the children's welfare.
"I know welfare had been called numerous times," she said.
"I strongly believe they should have done much more."
Ms Conley was remanded to appear in Beenleigh Magistrates Court on December 11.