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A second boy was arrested in connection with the death of teacher Ann Maguire, it has emerged.
The 15-year-old was questioned by police yesterday but released without charge.
Investigators are understood to have looked at messages on social media websites.
A spokesman for West Yorkshire Police said: “A 15-year-old male was arrested on Thursday morning in connection with the investigation but has since been released without charge.”
Another 15-year-old boy, who cannot be named for legal reasons, appeared at Leeds Crown Court today charged with Mrs Maguire’s murder.
The teenager appeared by video-link and was remanded in custody.
There was no application for bail and he was sent to a youth detention facility with a provisional trial date set for 3 November.
The Spanish teacher, 61, was months away from retiring when she was attacked in the classroom in front of terrified pupils on Monday at Corpus Christi Catholic College in Leeds.
Her husband and two daughters laid flowers at the school gates yesterday and held hands as they read some of the hundreds of tributes left by pupil and staff.
Earlier they had watched the teenager accused of stabbing her to death appear at Leeds Youth Court .
Donald Maguire stared straight at the youth as he was led into the glass-fronted dock and clutched the hands of his daughters, Emma and Kerry, throughout the hearing in the packed courtroom.
In pictures: Leeds school mourns Ann Maguire's deathShow all 18 1 /18In pictures: Leeds school mourns Ann Maguire's death In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Steve Mort, head teacher of Corpus Christi Catholic College, reads the hundreds of tributes left in honour of slain teacher Ann Maguire in Leeds
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Keiran Sykes, the deputy headteacher of Corpus Christi Catholic College, reads the hundreds of tributes left in honour of slain teacher Ann Maguire in Leeds
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Amanda Gledhill, a former pupil of Corpus Christi Catholic College, grieves next to the hundreds of tributes left in honour of slain teacher Ann Maguire in Leeds
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A photograph and flowers hang on the fence outside Corpus Christi Catholic College in tribute to slain teacher Ann Maguire in Leeds
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A candle burns next to a book of condolence for teacher Ann Maguire at Corpus Christi Catholic Church in Neville Road in Leeds
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A crucifix and school tie hang on the fence outside Corpus Christi Catholic College in tribute to slain teacher Ann Maguire in Leeds
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A drawing outside Corpus Christi Catholic College in Leeds, after much loved teacher Anne Maguire was stabbed to death in front of her pupils
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Monsignor Paul Fisher conducts a mass for members of the local community attending Corpus Christ Catholic Church to pray and pay their respects to teacher Ann Maguire in Leeds.
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Flowers are left outside Corpus Christi Catholic College in Leeds, after much loved teacher Ann Maguire, 61, was stabbed to death yesterday in front of her pupils.
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A note left outside Corpus Christi Catholic College in Leeds, after much loved teacher Ann Maguire, 61, was stabbed to death yesterday in front of her pupils.
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Flowers are left outside Corpus Christi Catholic College in Leeds, after much loved teacher Ann Maguire, 61, was stabbed to death yesterday in front of her pupils.
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A nun comforts students outside Corpus Christi Catholic College in Neville Road, Leeds, where a female teacher was fatally stabbed
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In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A school football shirt, signed by pupils, hangs on the gate
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In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death School head teacher Steve Moat, and the school's head boy and head girl lay flowers in Corpus Christ Catholic Church
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In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Messages and floral tributes including a photograph of Ann Maguire
In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A nun comforts people outside Corpus Christi Catholic College
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In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death A pupil looks at floral tributes at Corpus Christi Catholic College
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In pictures: Leeds school mourns Ann Maguire's death School mourns teacher's death Monsignor Paul Fisher conducts mass for members of the local community
PA
The boy, whose right arm was in plaster, nodded to his own parents as he walked into court.
The family paid tribute to Mrs Maguire in a statement released through West Yorkshire Police.
It said: “Our beautiful Ann, our shining light, she brightened the world for so many of us.
”A loving wife, the best mother, a treasured sister, a true friend. This horrific happening has robbed us of all of this and so much more.”
Additional reporting by PA