A sixth form college in Eastleigh, Hampshire was on lockdown after a person with a knife was reportedly spotted on the grounds.
Barton Peveril College was at the centre of a police operation after the lockdown and reports of students taking shelter in a gym.
School staff said they followed lockdown procedure and that the school campus was now safe. Barton Peveril confirmed to the Mirror that the incident occurred at the rear of the property.
One student said they were still unsure what happened, and that they suddenly found themselves surrounded by people running.
Preferring to remain anonymous, they told the Mirror: "Honestly I don’t really know what happened still.
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Students and parents took to social media to say how scared they were"I was walking to find one of my friends and then I heard someone scream outside so I looked out the window and people were running inside the buildings and security was shouting at people to go inside.
"Everyone was really confused so we just kinda locked ourselves in a classroom as teachers weren’t directly with us."
Hampshire Police said in a statement: "We were called at 2.20pm today, 9 March, to Barton Peveril College in Eastleigh after reports of a person with a knife inside the grounds.
"Officers attended and worked with staff at the school, at this time no injuries have been reported and no weapon has been located."
Nearby roads were also reportedly shut.
Multiple parents said their children reported a "gang of lads" wearing balaclavas at the time of the incident, although police have yet to reveal any more details.
One parent said her son had been in Eastleigh College, next door to Barton, at the time when armed officers swooped on the grounds and stopped him from leaving.
"They rushed all the kids back inside into the refectory with all the shutters down so they assumed it was happening at their own college," she said.
"It was only when I saw it on the news that I realised it was Barton and not Eastleigh College that was involved."
Another mum, whose daughter was barricaded inside Barton Peveril, told The Mirror: "They are out of lockdown have been for a while but me and my husband won't be sending our daughter back till they can prove they've tightened up security."
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Principal Rob Temple told the Southern Daily Echo: "We are aware that there was an incident at the back of the college this afternoon.
"We followed our lockdown procedures to ensure the safety of our college community.
"The police have reassured us that this was an isolated incident and the college campus is safe.
"Lessons are now continuing as planned and the college is open as normal tomorrow."
During the incident, one student took to social media to say there were "s******g it."
They said:" Idk what’s going on but my college is in lockdown rn and someone’s been stabbed and i’m s******g it."
They later confirmed they had been let out of the campus safely.
Local media reported another mum saying her daughter was messaging inside the college.
She told the Echo: "My daughter is messaging me from BP College.
"She saw about six boys not from the school chasing a lad and it looked bad.
"She raced to her classroom and was put into lockdown.
"She sat on the floor with the lights out and the door locked. Armed police were roaming the building.”
She added: “She has been made to go back to class and she is very shaken."