A machete has been found near a sixth form college that an armed gang stormed for a "pre-arranged fight".
The weapon was found by a police dog in a search after the disorder at
Runshaw College in
Leyland, Lancashire, on Monday.
Six people were arrested after police were tipped off that a group from
Manchester was heading to the college "with weapons".
Footage on social media appears to show students fleeing masked men.
The gang of around 12 young men - some brandishing knives wearing balaclavas and face masks - arrived at the college at about 16:00 GMT to confront a rival group.
Three men in a parked car were arrested nearby. A fourth person who made off on foot was also arrested.
Two more were held on Monday evening, with one picked up in a car on the M55 and one arrested in Preston.
A 17-year-old student was "nicked on the arm" during an altercation in the college grounds. He was treated in Chorley Hospital but his wound was not serious.
At the scene - Mike Stevens, BBC Radio Lancashire
Regular patrols are visible in the vicinity of the college this morning, as police work to reassure students.
Officers say their focus will now move to the investigation and they will be speaking to the six people in custody over the course of the day.
They are also keen to hear from anybody who witnessed what happened or has any mobile footage of the incident.
The MP for South Ribble Seema Kennedy has raised the issue with the Home Secretary.
A search was carried out after reports of a machete-style knife being used in the attack.
Lancashire Police Dog Unit said on Facebook: "It didn't take the team long to recover the weapon and other pieces of valuable evidence."
Ch Insp Gary Crowe, of Lancashire Police, said: "We believe this was a targeted attack in that we think the group have gone to find someone and a separate student has received a minor injury.
"This was not a random attack.
"This a very specific incident and a personal issue between a couple of people involved."