Jersey stabbings: Six die in knife attack
Police say a man, two women and the children were attacked at a flat in a secluded part of the capital, St Helier, on Sunday afternoon.
A 30-year-old man, who had emergency surgery after the attack, has been arrested in connection with the deaths.
Police have not named the dead but say they lived in Jersey. Witnesses believe they were all related.
Officers were called to Upper Midvale Road at 15:00 BST on Sunday after reports of an incident at a flat in Victoria Crescent, which spilled outside on to the street.
Forensic officers have been examining the scene as police interview a number of witnesses to try to identify the victims.
Meanwhile, they are holding the suspect in police custody at Jersey General Hospital where he is recovering from surgery.
'Complex investigation'
States of Jersey Police head of crime services Stewart Gull, who is leading the inquiry, said: "Clearly this complex investigation is in its very early stages as we try to establish exactly what happened.
"We are mindful, too, of the impact of any such serious and tragic incident on the local community, and we have police officers in the area to support the investigation and local people."
Mr Gull, who led the inquiry into the murder of five Ipswich women in 2006, admitted he was shaken by the Jersey incident and said it had been "pretty traumatic" for emergency services staff called to the scene.
"Dealing with multiple deaths of men, women and particularly young children, it has shaken the force but the officers who initially responded were tremendously professional," he said.
"Jersey is an incredibly safe island, probably one of the safest places in the western world. Incidents of this nature are an extremely rare occurrence."
He added that he was unable to confirm the victims' nationalities, speculate as to their relationship with each other or give the ages of the children.
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