Lucy Letby has been interviewed by police in prison under caution as part of ongoing investigations into more baby deaths at two hospitals, Cheshire Constabulary has confirmed.

The force said it had “recently” spoken to the former neonatal nurse over deaths at and non-fatal collapses at the Countess of Chester Hospital and Liverpool Women’s Hospital.

Letby was convicted of the murders of seven infants and the attempted murder of seven more at the Countess of Chester between 2015 and 2016.

It is understood she has not been previously been interviewed over deaths at the Liverpool hospital – where she worked 30 shifts on two placements between 2012 and 2015.

The Cheshire police statement confirming Letby had been quizzed over more baby deaths followed reporting in the Daily Mail. The force also said more information would be released “at the appropriate time”.

Letby, 34, from Hereford, is serving 15 whole-life orders after she was convicted at Manchester Crown Court last year of murdering seven infants and attempting to murder seven others, with two attempts on one of her victims, between June 2015 and June 2016.

Following her trial, Cheshire Constabulary revealed officers were investigating the time she spent on two placements in Liverpool Women’s Hospital in 2012 and 2015.

Detectives are examining Letby’s entire career, an effort which involves reviewing more than 4,000 admissions of babies into neonatal units where she was present.

In October, BBC Panorama uncovered potentially life-threatening incidents occurred on almost a third of Letby’s shifts in Liverpool.

In one November 2012 case, a baby boy collapsed and water was later found in his breathing tube – something highly unusual. The clinical notes confirmed that the nurse looking after him was Letby.

The programme also saw evidence that may have shown a baby boy was poisoned with insulin whilst in her care at the Countess of Chester Hospital. This case was not part of the trial.

Her crimes are currently being examined at the Thirlwall Inquiry, which heard last month from the lead paediatric consultant at the Countess of Chester who originally raised the alarm about her.

Dr Stephen Breary told the inquiry at Liverpool Town Hall: “On reflection I think it’s likely that Letby didn’t start [to] become a killer in June 2015, or didn’t start harming babies in 2015.”

In September, a barrister representing the families of 12 babies said that Liverpool Women’s Hospital had conducted its own audit into Letby’s time there.

Richard Baker KC told the inquiry that babies’ breathing tubes were dislodged at an “unusual” rate while she was on shift. They became dislodged in around 40% of the shifts, compared to this “occurring generally in less than 1% of shifts”.

But there has also been significant debate over the science used in the case against Letby – a number of experts have challenged the medical evidence used to convict her.

Letby’s new legal team say they also take a different view of the new evidence – and have said they plan to take her case to the Criminal Cases Review Commission next year to apply for it to be sent back to the Court of Appeal.

She has previously lost several appeals against her convictions.

The Thirwall Inquiry has also heard from the hospital’s bosses in recent days, some of whom are speaking publicly about the case for the first time.

Former chairman Sir Duncan Nichol told the inquiry that his decision to not invite the doctors who suspected her to an important meeting was “a big personal failure”.