Bomb disposal teams called to 14 NI schools
Fourteen schools across Northern Ireland have contacted authorities in the past week over a lab chemical that can explode if not stored correctly.
A rising number of schools have also had to call in bomb disposal teams to carry out controlled explosions.
The PSNI said they expect more such calls in the days ahead.
Earlier in the month, guidance was issued nationally, with teachers urged to check if laboratories keep 2,4 dinitrophenyl hydrazine (DNP).
The chemical, also known as 2,4-DNP, is used in A-level chemistry lessons and is safe if stored correctly, but can become dangerous if it is allowed to dry out.
It is known to pose a risk of explosion by shock, friction or fire and is usually kept inside a larger container holding water.
The principal of St Ronan's College in Lurgan said explosive disposal experts came to the school earlier this week.
In schools elsewhere in the UK, pupils were evacuated as controlled explosions were carried out on the school premises.
However, Michele Corkey said the chemical was removed from St Ronan's with no such commotion.
"We contacted the disposal unit, who came to the school very quietly and inconspicuously and took it away," she said.
"We were told that we were the sixth school to have called them that morning, so we know there are a lot of other schools affected by this, but I'm sure, like ourselves, it was a non-event.
"It's part of the A-Level exam, and thankfully St Ronan's have never have any issue with it.
"All chemicals have the potential to be dangerous, so we treat them with due respect, but occasionally we do get advice from outside agencies to say what procedures we need to follow if we're using them."