Six women have been arrested in connection with the suspicious death of a one-year-old boy at a nursery.
West Midlands Police said a criminal investigation was launched after the toddler died at Fairytales Day Nursery, in Bourne Street, Dudley, on 9 December last year.
The nursery was closed by Ofsted along with other linked premises on 14 December after the watchdog said "children may be at risk of harm" and suspended its registration.
The force said three women aged 20, 23 and 50 were arrested on 16 December on suspicion of gross negligence manslaughter and later bailed.
Three more women aged 51, 53 and 37 were detained on Wednesday - two on suspicion of corporate manslaughter and one on suspicion of gross negligence manslaughter.
In a statement, police said: "We are treating the death of a one-year-old boy on December 9, at a Dudley nursery as suspicious and an investigation is under way."
The force added: "The boy's family is being supported by specially trained officers.
"A post-mortem has taken place but further tests will be conducted to establish the exact cause of death."
Two ambulances, trauma doctor and air ambulance sent to scene
West Midlands Ambulance Service said medics were called to premises in Bourne Street at 3.19pm and two ambulances, a trauma doctor and an air ambulance were sent to the scene.
"On arrival crews found a child in a critical condition," the ambulance service said. "Medics commenced advanced life support which continued en route to Russells Hall Hospital (Dudley) by ambulance."
However, the youngster died despite the efforts of medical personnel.
'We believe children may be at risk of harm'
An Ofsted report published in February last year found provision at the multi-award-winning nursery to be good overall.
However, inspectors returned on 15 December last year after Fairytales' management told the watchdog of "a serious incident involving a child in their care" at the Bourne Street site on 9 December.
The provider, which runs two nursery sites, is legally obliged to tell Ofsted if there has been a "serious accident, illness or injury to, or death of, any child while in their care".
In a report published on 22 December, the watchdog said it had suspended the nursery's registration on 14 December having "received concerns that the provider was not meeting some of the safeguarding and welfare requirements".
"We suspended the provider's registration because we believe children may be at risk of harm," the report said.
During a visit on 15 December, inspectors found the nursery had failed to tell authorities about a change of manager, "which is an offence", and uncovered welfare shortcomings, particularly in the care of babies in the sleeping room.
Ofsted report highlights 'risks in the baby room'
Setting out what actions which, by law, needed to be taken at the site by 13 January, Ofsted directed the nursery to "ensure at least half the staff who care for babies have received training that specifically addresses the care of babies".
It must also "demonstrate how you will ensure sleeping babies are frequently checked to ensure that they are safe", as well as "review and implement sleeping arrangements to ensure children are placed down to sleep safely in line with latest government safety guidance".
Ofsted said all staff must have the correct "qualifications, training, skills, knowledge, and a clear understanding of their roles and responsibilities with regards to sleeping children" and the nursery must "take all reasonable steps to ensure children in your care are not exposed to risks, paying particular attention to risks in the baby room".
It said the provider must also "ensure risk assessment is effective and identify aspects of the environment that need to be checked on a regular basis... and how the risk will be removed or minimised".