A woman has been arrested on suspicion of child neglect after the unexplained death of an eight-year-old girl.
Police are investigating circumstances surrounding the “sudden death” of the girl at Lampeter, in Ceredigion.
It comes as public health officials confirmed they are examining links between possible Strep A infections and a child’s death in the town.
Dyfed-Powys Police said a 33-year-old woman has been released as inquiries continue.
Police said the girl died at Maes-y-Deri in Lampeter on the evening of 22 December.
An arrest was then made the following day in connection with the death.
Public Health Wales said on Wednesday it was looking into possible links to a rare complication of Strep A infections.
It follows more than a dozen confirmed deaths of children with strep A since September, including Hanna Roap, seven, from Penarth in the Vale of Glamorgan.
Dr Graham Brown, consultant in communicable disease control for Public Health Wales, said: “Public Health Wales is working with Hywel Dda University Health Board and Ceredigion council following the death of a child in Lampeter.
“We offer our deepest condolences to the family, friends and all those affected. Public Health Wales cannot comment on individual cases.
“We are investigating links to Invasive Group A Streptococcal disease (iGAS), a very rare complication of Group A Streptococcal infection.
“While we understand that parents are likely to be worried, cases of iGAS remain rare in Wales, and children have a very low risk of contracting the disease.”
Most often, symptoms of Strep A are mild, with a sore throat or a skin infection that can be treated with antibiotics.
But Strep A can cause a range of symptoms and one is Scarlet Fever, which mostly affects young children, and again needs antibiotics.
Very rarely, the illness can lead to the invasive form of the infection, when the bacteria gets past the body’s immune defences.