A teenager was captured on camera holding a large knife in Preston city centre.
The images showed a young man in a black jacket, clutching a long blade, walking with another youth on Church Street at around 5.30pm on Wednesday.
Since then, Preston police say they have identified the youngster in question and have removed the photos from their Twitter account.
A Lancashire police spokesman said: “Following the CCTV picture appeal, we identified a person we wanted to speak to following reports of a teenager with a knife in Preston city centre.
“The social media appeal was subsequently cancelled and inquiries are ongoing.”
The appeal was launched as part of a day-long Twitter event to give residents a flavour of what Preston officers do on a day-to-day basis.
One tweet told of a young person who had been assaulted by multiple adult family members; another revealed that a young man had been assaulted by a group of older boys outside McDonalds at Deepdale, and another told of officers called to help a woman who had self-harmed.
In one incident, officers stopped a car and arrested the driver for driving under the influence of drugs. They later tweeted a picture of the drugs found in the vehicle.
During the day police in the city also had to deal with a number of missing people and interview prisoners.