An unsafe chemical that has seen some schools in the UK call in bomb disposal experts to carry out controlled explosions was the reason why a Calderdale school was evacuated.
Lightcliffe Academy in Stoney Lane was closed at lunch time on Monday for health and safety reasons.
A spokesperson for West Yorkshire Police said: “Police attended a school in Lightcliffe, Halifax on Monday to assist in the disposal of a school chemical contained on site as part of a planned operation.
“The substance is a chemical kept on site in some schools for use in science lessons.
“It has been withdrawn from premises in certain cases as a precaution following new national advice over its storage.
“Police assisted the local education authority in safely resolving the matter with the minimum of disruption.”
Schools have been acting in response to government advice from the Consortium of Local Education Authorities for the Provision of Science Equipment (CLEAPSS) to check for 2,4-DNP.
A government advisory note sent out on 28 October said CLEAPSS had “recently received a number of calls regarding the chemical.
A warning to schools on the CLEAPSS website read: “If there is no water in the outer container or the reagent bottle has not been placed inside an additional container you must assume that the material has dried out meaning that an additional risk is present.”
Principal Tom Rothwell said: “We were alerted to the fact that a chemical substance previously used in science was potentially unsafe.
“Police advice was that it needed dealing with immediately and that a significant part of school was cordoned off until this was done.
“Therefore we put our emergency evacuation procedures in place.
“The students and staff responded in a safe and calm manner.”