Police in Austria have urged people to be vigilant after a sample of HiPP baby food was found to contain rat poison.

Police in the eastern region of Burgenland said the poisoned jar of carrot and potato purée had been reported by a customer and that their baby had fortunately not consumed the food.

The jar had apparently been tampered with, police said. Authorities believe at least one more poisoned jar is in circulation and have issued guidance on how to recognise tampered jars.

They have not confirmed that the cases involve an alleged extortion attempt. But the police statement said the warning had come from German investigators and tampered jars had also been seized in the Czech Republic and Slovakia.

On Saturday, HiPP recalled its entire range of jarred purées sold in Spar supermarkets in Austria, saying consuming them may be potentially "life-threatening".

The German-based company said the recall of baby food jars at Spar Austria was "not due to a product or quality defect on our part" - and that jars had left its factory in "perfect condition".

"The recall is related to a criminal act that is being investigated by the authorities," it said on its website.

"As part of ongoing criminal investigations, isolated cases of tampered HiPP baby food jars have been seized - as previously reported in Austria, now also in the Czech Republic and Slovakia.

"The responsible authorities determined upon examination of these jars that they contained rat poison."

Spar has also removed the brand's baby food from its stores in other countries as a precautionary measure.

Austrian authorities have told consumers to look out for damaged or open lids, a missing safety seal, an unusual or spoiled odour, or a white sticker with a red circle on the bottom of the glass jar.

The Austrian Agency for Health and Food Safety warned parents whose babies had consumed the brand's food to consult a doctor if their children showed signs of bleeding, extreme weakness or paleness.

Customers have also been asked not to consume HiPP jars purchased at Eurospar, Interspar and Maximarkt, and to return them for a refund.

There are more than 1,500 Spar shops across Austria.

Police previously stressed baby food sold in other shops remained unaffected by the recall.

HiPP's baby formula was also unaffected.

Retailers in the Czech Republic and Slovakia have also preemptively removed all HiPP baby food jars from sale.

The incident comes just a few months after two other baby brands had to issue wides-cale recalls of infant formula over contamination fears.

In January and February, Nestle and Danone issued recalls of their baby formula brands in more than 60 countries, including in the UK, after babies fell ill.

Specific batches were understood to have been contaminated with toxin cereulide, which can trigger nausea and vomiting when consumed. The toxin is not destroyed by cooking or when making baby milk.

The UK's Health and Security Agency (UKHSA) said in February that at least 36 infants in Britain had suffered food poisoning due to contaminated baby formula. None of the infants' conditions were life-threatening, the UKHSA said.