A female healthcare professional in England has been arrested on suspicion of murdering eight babies and the attempted murder of another six babies.

Key points: Police investigating the deaths of 17 babies between March 2015 and July 2016

Police investigating the deaths of 17 babies between March 2015 and July 2016 'Operation Hummingbird' also looking into 15 non-fatal collapses of babies

'Operation Hummingbird' also looking into 15 non-fatal collapses of babies Parents are being kept updated and supported by specially trained officers

The arrest 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, south of Liverpool, between March 2015 and July 2016.

A non-fatal collapse is when a baby's condition severely and suddenly declines but the infant survives.

Detective Inspector Paul Hughes said the woman was arrested early on Tuesday (local time) and remained in custody.

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

"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."

The investigation, dubbed Operation Hummingbird, was launched in May 2017 and originally focused on the deaths of 15 babies between June 2015 and June 2016, as well as six non-fatal collapses.

In July 2016, the Countess of Chester 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.

"We have seen in some of our most poorly babies [those with high dependency needs] an increase in neonatal mortality rates for 2015 and 2016 compared to previous years," the hospital said in a statement.

An independent, clinical review into the hospital's neonatal service in late 2016 found there was no single cause or factor to explain the baby's deaths.

In a statement published 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.