A criminal enquiry has been launched in France after a six-year-old boy ‘left to roam around a maternity unit’ allegedly killed a newborn baby. The horror unfolded at the Jeanne-de-Flandre Children’s Hospital in the northern city of Lille.

It was there that a baby identified as Zayneb-Cassandra – who was born premature, at 7.5 months, to a 23-year-old woman, earlier this month – was declared dead on Tuesday. She suffered a traumatic brain injury last Friday after allegedly being dropped on the floor by the boy ‘who treated her like a doll,’ said an investigating source.

Despite being reported as a ‘disruptive presence’ in the hospital, the boy was found alone with the unconscious baby in a neonatal unit.

The baby was her mother’s first child, and she was delivered by cesarean section, said the  investigating source.

‘The delivery went very well, but the little girl was premature, so she was taken to a neotatal unit, while her mother remained in a maternity ward.’

The ‘disruptive six-year-old’ – the son of another mother who was in a maternity ward – was spotted wandering around the hospital unattended.

Zayneb-Cassandra’s grandmother told the Voix du Nord newspaper: ‘The boy would arrive at 7am and spend all day running up and down the hallways.

‘All the mothers were complaining, and a nurse even warned the child’s mother that there was a problem. He was entering the other rooms.

‘He also entered Zayneb’s room for the first time. He said she looked like a doll, and my husband, who was there, took him out.’

Last Friday, Zayneb’s mother was signing discharge papers, when ‘all of a sudden, the family received a call from a ward manager, saying they needed to come right away – a little boy had been playing with the baby, who had fallen.’

According to the family, who cite another mother in a neighboring room, ‘a loud bang’ was heard when the baby’s head connected with the ground.

Zayneb was found unresponsive on the floor, next to the six-year-old, who was on a chair.

‘It seems he tried to grab her by her nappy, and she fell on her head,’ said Zayneb’s grandmother.

The baby was rushed to intensive care, but she was declared dead on Tuesday, after suffering ‘a serious a brain injury.’

An investigation has been opened by the juvenile unit of the Lille Judicial Police Service, in conjunction with local prosecutors.

‘Investigations are currently underway in this case,’ said a spokesman for  Lille prosecutors.

The hospital also announced the opening of ‘an internal administrative investigation’.

A spokesman said: ‘This human tragedy has deeply affected the staff and teams of Lille University Children’s Hospital, as well as the other families present.’