The coffin was reported missing from the Westfriedhof graveyard in Cologne on Monday of last week. Investigators speculated the coffin could have been stolen, possibly by a motorcycle gang, the Rheinische Post newspaper reported on Wednesday.
Graveyard officials at first categorically denied that the body could have been burnt by mistake – until an investigation showed it had.
When officials from Cologne's Office For Public Spaces looked into the case, they discovered another coffin containing a body which, according to documents, was supposed to have been burnt.
It then emerged that the woman's remains had been mislabelled and confused with those of the other body intended to be cremated.
"Mistaking a number and burning the wrong body should not be allowed to happen in this highly sensitive domain. But failing to discover the correct body despite several checks is unforgivable," Manfred Kaune, head of Cologne's Office for Public Spaces, told the Kölner Express newspaper.
"It's an absolute mess, which will have consequences, including for members of staff," Kaune said.
City authorities said they would like to get in touch with the family in order to discuss the next steps.
The Office for Public Spaces said in a statement on their website: "The city of Cologne expresses the utmost regret at this mistake and apologizes to family and friends of the deceased, who have to endure added suffering due to the mistake. We will do everything to prevent this from ever happening again."
Follow us on Twitter @thelocalgermany
Like The Local Germany on Facebook