A neonatal nurse in Britain has been arrested on suspicion of murdering eight babies and the attempted murder of another six in a hospital scandal affecting dozens of families.

The arrest of the woman, identified by British media as Lucy Letby, 28, is part of an ongoing investigation into the deaths of 17 babies and 15 non-fatal collapses at the Countess of Chester Hospital in Chester between March 2015 and July 2016.

“This is a highly complex and very sensitive investigation,” Detective Inspector Hughes said.

“As you can appreciate, we need to ensure we do everything we possibly can to try to establish in detail what has led to these baby deaths and collapses.

“Parents of all the babies are continuing to be kept fully updated and are being supported throughout the process by specially trained officers.

“This is an extremely difficult time for all the families and it is important to remember that, at the heart of this, there are a number of bereaved families seeking answers as to what happened to their children.”

Cheshire Police are investigating the deaths of 17 babies and 15 ‘non-fatal collapses’. Photo: AAP

According to The Sun, Ms Letby’s arrest “stunned colleagues because she is regarded as a champion of the children she cares for”.

She is reportedly a member of 14 groups related to helping sick children and helped a fund-raising campaign to build a new $5.3 million baby unit at the Countess of Chester Hospital.

In a past interview with a local paper, Ms Letby, who said she qualified as a children’s nurse in 2011, posed on a ward holding a baby’s onesie and described her love of the job.

“My role involves caring for a wide range of babies requiring various levels of support,” she said.

“Some are here for a few days, others for many months and I enjoy seeing them progress and supporting their families.”

The Duchess of Cornwall visited the Countess of Chester Hospital in 2014. Photo: Getty

Jordan Sands, who knew Ms Letby through a mutual friend, told The Times: “She was quite awkward and geeky but seemed like a kind-hearted person.”

A neighbour of Ms Letby’s parents, John and Susan, told The Times: “Lucy is so dedicated to her job. I just truly can’t believe it. She was a good little girl. She was a delight.”

Police launched a probe dubbed Operation Hummingbird into the neo-natal unit at the Countess of Chester Hospital last May.

It originally focused on the deaths of 15 babies between June 2015 and June 2016, as well as six non-fatal collapses.

The hospital trust raised the alarm itself following the high number of fatalities between March 2015 and July 2016.

According to The Times, experts from the Royal College of Paediatrics and Child Health said in an independent 2016 report that the hospital had not investigated infants’ deaths thoroughly enough.

“Consultants noted that several of the infants collapsed unexpectedly and had been surprisingly unresponsive to resuscitation,” their report said.

One baby collapsed the same way on three different nights for no clear reason.

In July 2016, the hospital announced it was changing its admission arrangements for its neonatal unit to focus on lower-risk babies who were born after 32 weeks.

It also closed three intensive care cots.

On Tuesday, medical director Ian Harvey said the hospital was continuing to support police with their ongoing investigation.

“Asking the police to look into this was not something we did lightly, but we need to do everything we can to understand what has happened here and get the answers we and the families so desperately want,” he said.

–with agencies