German police say they're seeking one or more people who threatened to poison food sold by German companies unless they're paid millions of euros (dollars).

Officials in Konstanz, on Germany's southern border, said Thursday the blackmailer or blackmailers alerted them Sept. 16 that five jars of baby food at shops in nearby Friedrichshafen had been manipulated.

A state consumer protection ministry official said the substance detected was ethylene glycol, used in antifreeze products and brake fluids, which is toxic and fatal in large quantities.

They said an email was sent to authorities and companies threatening to poison unspecified food at branches of German retailers inside the country and beyond if they're not paid more than 10 million euros ($11.8 million) by Saturday. Officials didn't specify which retailers were targeted.

Authorities have urged the public to be vigilant about signs of tampering, releasing a surveillance camera image of the suspect, a man aged around 50 wearing glasses and a white cap.

"We take this threat very seriously," said chief prosecutor Alexander Boger in a televised news conference.

Constance Deputy Police Chief Uwe Stuermer warned of a criminal "without scruples" but also said that, given heightened vigilance, "there is no reason to panic."

The blackmailer had demanded 10 million euros ($12 million) from a retail chain, reported Bild daily. The threat was made in an email that was also sent to a consumer protection group and police.

It did not specify which type of food would be poisoned, or in which region or stores the products would be placed.