Health authorities have issued a public warning after five people were hospitalised in Brisbane’s south in the past week after apparently ingesting rat bait.

Amid fears the food at one or more takeaway outlets has been contaminated with rat poison, Queenslanders have been warned to be alert for concerning symptoms such as excessive bleeding.

Queensland Health issued an internal alert to staff on Saturday warning them to look out for symptoms related to consumption of brodifacoum – a widely used rat poison.

It came after five patients, one a child, presented to the Queensland Children’s Hospital, Logan Hospital and Princess Alexandra.

“Thankfully, all are fine and receiving treatment,” Chief health officer Catherine McDougall said on Monday.

“Clinicians have been asked to monitor for presentations with similar symptoms. This is routine when patterns in patient presentations are identified.”

Brodifacoum is commonly found in rat poison. It reduces vitamin K, which is essential for blood to clot. If ingested by humans, it can cause bleeding gums, easy bruising and blood in urine or stools.

Treatment typically involves doses of vitamin K therapy, and can take weeks.

Clinicians have also been urged to monitor patients who have bleeding-related symptoms that cannot be otherwise explained.

Professor Paul Griffin, the director of infectious diseases at Mater Health, said symptoms of rat poisoning could take “many days” to be noticed, and warned people not to be complacent.

“There’s a strong suggestion, from where these people are presenting, that the clustering is on the south side [of Brisbane],” he told the Nine newspapers.

“But because it can take a long time for the effects to be noticed, we certainly don’t want people in other areas to be complacent or assume that we won’t see a case somewhere potentially unexpected.”

Health authorities suspect the patients have ingested the poison via contaminated products served at a fast food outlet in Logan.

“The simple message now is that anyone who’s bleeding unexpectedly or more than they might expect, especially if you’ve been in the vicinity of where these cases seem to be clustering, I’d certainly go and get checked out,” Griffin said.

“The more cases we find, the greater the probability of cross-referencing where the exposure might have been, so we can hopefully track down [the source] and get to the bottom of what’s happened.”

Queensland Health Minister Tim Nicholls said the first warning was issued on Friday night and there had been no more cases since.

“We don’t know the source of it yet. I know there has been speculation, but we have not been able to identify the point source of the poison,” he told the ABC

“The health service is continuing to investigate to find out where it came from. But our primary concern is making sure those involved are well on their way to recovery and are in a position to be interviewed.”

Nicholls said everything possible was being done to locate the source, which included examining the possibility that rat bait had contaminated food at a restaurant or takeaway outlet.

Anyone with concerns about their health should see their doctor, go to an emergency department or call 134 325.