An Ipswich school went into lockdown after police were called to an incident. 

Ipswich Academy used its invacuation procedure during an "unprecedented event" at the school on Monday. 

At about 3.10pm the school received an email that triggered the lockdown and the incident has been reported to police. 

Students were kept safe until officers confirmed it was safe for them to leave. 

A letter sent by headteacher Samuel Fox to parents and guardians reads: "We are writing to inform you that we used our invacuation procedure at the end of the day, leading to a delay in the departure of the students. 

"As you may be aware, all schools are legally required to have practices and procedures in place to respond to various situations of risk.

"Ipswich Academy students have practiced these regularly. 

"The safety of our students is at the heart of all we do so we would like to take the opportunity to thank them for the calm and focused way in which they responded to this unprecedented event."

Ipswich Academy and Suffolk police have been approached for more information.