A FACEBOOK message led to a punch-up that left a police officer with a minor hand injury.
A private birthday party at Sobar, King Street, Clitheroe, on Saturday was posted on the social media site and more than 1,000 turned up instead of the 250 expected.
Most of the crowd had dispersed when police arrived but four young men were involved in a fight in the street outside the bar.
A 19-year-old man was questioned on suspicion of assault and released on police bail, and another 19-year-old man was given a fixed penalty notice and released.
Two men aged 18 and 23 were released after a police caution.
After the incident, Lancashire police warned people not to spread word about parties on Facebook.