A British female healthcare worker has been arrested on suspicion of murdering eight babies and trying to murder six others after an investigation into deaths at a neonatal unit in northern England, police said on Tuesday, Reuters reported.

The arrest came after an inquiry into the deaths of 17 babies and 15 “non-fatal collapses” between March 2015 and July 2016 at The Countess of Chester Hospital’s neonatal unit.

Police, who launched their investigation in May last year, would not give further details about the arrested woman, who was simply described as a healthcare professional. Hughes said the investigation was still “very much active”.