Australian police are investigating the deaths of eight children after their bodies were found in a home in the tropical northern city of Cairns on Friday.

The children, aged between 18 months and 15 years, were found at 11.20am (1.20am Irish time) in the suburb of Manoora, Queensland state police said in a statement.

A 34-year-old woman, who’s being treated for serious injuries in the hospital, is helping police with their inquiries, Detective Inspector Bruno Asnicar told reporters.

Det Insp Asnicar said police believed the woman was the mother of seven of the children.

“There is no formal suspect,” Det Insp Asnicar told reporters. “We are talking to a range of people. Anybody who has had any involvement in the past two or three days is a person of interest,” he said.

The children’s bodies were discovered by their 20-year-old brother, who is

now being comforted by family members, the Cairns Post reported.

The community has been told there is “no need for the public to be concerned about this other than the fact that it’s a tragic, tragic event”, and the situation is under control.

VIDEO: Cairns Detective Inspector Bruno Asnicar speaks about #Manoora deaths investigations. https://t.co/5IaHjZbXtx — QPS Media Unit (@QPSmedia) December 19, 2014

About 50 people gather for a candlelight vigil to remember the eight children stabbed to death in Cairns. pic.twitter.com/SZo0KGq42S — Kristy Sexton (@kristysexton) December 19, 2014 Ngatu Tenu is a friend of the family "It's devastating, everybody knows each other around here so it has hit us all" pic.twitter.com/PN5OTPCTIQ — Isaac Egan (@matosis) December 19, 2014

Superintendent Russell Miller said: “First of all I’d just ask that the community remain calm. Obviously it’s going to be a very complex investigation, it’s going to take time.”

He added: “There’s no indication whatsoever that it will be wider spread in the community. But there is some very unhelpful social media posts — for want of a better word, out there, that aren’t assisting and will obviously generate some unrest if they continue.”

He said “significant numbers” of police are involved in the investigation, and called on the community to “remain calm”, saying: “I’m sure the community will support each other and that’s the biggest thing, and we’ll certainly provide the resources that they need to do that.

“I’d just encourage the community to lean on each other and seek support, but just remain calm and look after your mates, that’s a big thing.” Speaking about the police involved, he said: “It’s devastating any time of the year, and obviously some of the police who were on the scene earlier are young junior officers. So again, we’re providing the support to them that they need as well from within our own systems.”

A “community recovery plan” is being put in place to provide support to family members and friends.

Lisa Thaiday, who said she is the injured woman’s cousin, said one of the woman’s other sons, a 20-year-old, came home to find his brothers and sisters dead inside the house. “I’m going to see him now, he needs comforting,” Ms Thaiday said. “We’re a big family ... I just can’t believe it. We just found out (about) those poor babies.”

Australian prime minister Tony Abbott released a statement calling the deaths “an unspeakable crime” while state premier Campbell Newman said he would ensure the emergency services workers who attended the scene would be given counseling if needed.

“As it stands at the moment, there’s no need for the public to be concerned about this other than the fact it’s a tragic, tragic event,” Det Insp Asnicar said.

“The situation is well-controlled.” He declined to comment on the relationship between the woman and the children, and warned that the confirmed number of deaths could be higher or lower than initially reported.

Police haven’t said how the children were killed, amid reports in local media that many were stabbed.

The incident is one of Australia’s worst mass killings and comes days after two hostages and a gunman were killed following a 16-hour siege in a Sydney cafe this week.

Mr Abbott said the nation was facing “trying days.”

“The news out of Cairns is heartbreaking,” Mr Abbott said. “Tonight, there will be tears and prayers across our country for these children.” The nation’s worst mass murder was at Port Arthur in Tasmania in 1996 when Martin Bryant shot dead 35 people.

Agencies