Two men were sent to hospital with bizarre injuries after shaking hands with an elderly woman on a a bus heading to Skegness from Lincoln.
The two males later discovered they had small wounds on their hands after the incident on the bus on August 6.
The woman left the bus at Horncastle and the men attended hospital, but their wounds were not serious.
Lincolnshire Police published an appeal on September 18 with an image of people they would like to speak to, who may have witnessed the incident.
The force said: “We would like to make clear that the people in these photographs are not being treated as suspects, but we would like to speak to them as they may have information relating to this incident.”
Anyone with information that may assist with the police investigation should contact them on 101 or via email at [email protected] quoting reference 447 of August 6.
It can also be reported through the independent charity Crimestoppers anonymously on 0800 555 111 or online here.