A self-styled Cookie Monster thief who took a large golden biscuit from outside a renowned German baked-goods maker to demand goodies for sick children appears to have returned the emblem.

A big golden biscuit wrapped in a red ribbon mysteriously appeared on a monument in front of Hanover University in northern Germany and police said they were checking if it was indeed the missing company symbol.

The removal last month of the 20kg golden biscuit from the front of the Bahlsen firm headquarters, which among other things produces Leibniz butter cookies, has made headlines since a ransom letter emerged.

As well as demanding biscuits for children in a hospital, the letter called for a 1000 euro ($1305) reward that Bahlsen had offered for the emblem's return to be donated to an animal shelter.

A photo of an unidentified person in a Cookie Monster costume, a character from the children's television series Sesame Street, was attached.

The costumed culprit reappeared in a second letter sent to the regional Hannoversche Allgemeine Zeitung on Monday.

That letter, made up of newspaper clippings, announced the return of the golden biscuit, stating: "Because Werni, like me, so loves the biscuit, and is now always crying and misses the biscuit so much, I'm giving it back."

The message was apparently referring to Werner Bahlsen, head of the company, which last week called for the golden biscuit's return and said it was ready to give 1000 Leibniz cookies to 52 social institutions.

The golden emblem, which resembles one of the biscuits, had hung outside the company, established in 1889, for around 100 years and reappeared on Tuesday hanging around the neck of a horse monument.