The trial of a 14-year-old girl accused of trying to murder two teachers and a pupil in a school stabbing has collapsed due to a “great irregularity in the jury”.

Teachers Fiona Elias and Liz Hopkin and a pupil at Ysgol Dyffryn Aman in Ammanford, Carmarthenshire, were taken to hospital after being stabbed on 24 April.

The girl, who cannot be named due to her age, pleaded guilty to three counts of wounding with intent, but denied three counts of attempted murder.

The jury at Swansea Crown Court began deliberations on Tuesday, but were discharged on Wednesday morning, with Judge Paul Thomas KC saying the trial had been “irretrievably compromised”.

The judge asked one member of the jury to stay behind as members of the public were told to leave the court.

A retrial is due to start on 27 January.

Mr Thomas said the collapse of this trial was due to “a great irregularity in the jury which we all agree has irretrievably compromised our ability to consider this matter”.

He added: “With the greatest of possible reluctance, I will have to discharge this jury.

“[It is] profound and very unsatisfactory to discharge the jury, especially for the 14-year-old who will have to stand trial again.”

On the day of the triple stabbing, emergency services, including two air ambulance helicopters, were called to the scene and a knife was recovered.

The three victims sustained non-life threatening injuries but Ms Hopkin, who was stabbed in the neck, had to be airlifted to hospital.

The school was locked down and remained closed the following day for investigations to take place.