The Rhine Main-based vendor noticed the small blue kernels in a carton of romaine lettuce but it was too late - already five cartons of romaine have been sold, according to Focus.
A delivery of 110 cartons of the salad from Italy resulted in 105 of them being destroyed, a spokesman from the regulatory agency in Frankfurt told the magazine's online service on Friday.
One carton was sold to a market in Offenbach, a suburb of Frankfurt. Four others were sent to a vegetable distributor and most likely sold to consumers.
As of Friday there were no reports of poisoning or injuries from the rat poisoning, the regulatory agency said. The Federal Office for Consumer Protection and Food Security warned against consuming the salad.
The poison appears as small blue kernels. The salad was sold to the flying traders Fliegende Handler in the Rhine Main area and to the Istanbul Market in Offenbach.