Queensland state minister Tim Nicholls, who laid a wreath at the site, said police had not yet explained the motive behind the killings.
“As a father myself with three children under 15, I can only imagine the grief this community is feeling as they come to grips with the events,” he said.
The dead children were reportedly discovered by the mother’s 20-year-old son when he arrived at the house in the Cairns suburb of Manoora on Friday morning.
Reports said a woman was heard screaming in the house on Thursday night, with Brisbane’s Courier-Mail saying she had shouted: “Don’t let them take away from us. God bless us. Forgive me for what I’ll do.”
A 13-year-old girl who walked a friend who lived in the house home on Thursday night said she had met the mother, who had given her money for a taxi ride home.
“She was saying stuff about God and other stuff,” she told Australian Associated Press. “She said: ‘Papa God gave me the power to do anything’.”