A review into mother and baby deaths and injuries at hospitals in Shropshire is examining more than 100 cases, it is understood.
In 2017, Jeremy Hunt ordered an investigation into maternity care relating to 23 cases at the Shrewsbury and Telford NHS Trust (SaTH).
That figure expanded to 40 but is now thought to include 104 families.
Meanwhile, the Care Quality Commission (CQC) has taken urgent action against the maternity department.
One mother whose daughter died at the trust said "it is time to get justice".
The trust said it "continues to engage fully" with health watchdog the CQC "during our current, ongoing inspection".
A specialist team led by Donna Ockenden is looking into the allegations that some babies born at the trust between 2000 and 2017 suffered avoidable harm due to errors by maternity staff.
In August a spokesperson for NHS Improvement said it had agreed "to consider additional historical investigations where women, infants and new-born babies had died or suffered harm".
At the time the trust said these were cases which were already in the public domain, but the BBC understands at least 104 families have now come forward wanting their cases to be considered.
Dr Kathy McLean, Executive Medical Director and Chief Operating Officer of NHS Improvement, said: "At this stage, we are unable to confirm how many historical cases will be considered under our independent review.
"We are examining in detail anything that may be relevant, ensuring that possible duplication is taken into account.
"Also, it is important that in any historical investigations that we consider, appropriate consent from the family members is obtained in advance."
Professor Ted Baker, CQC's Chief Inspector of Hospitals, confirmed it is taking further enforcement action against SaTH.
It follows an inspection last month, which highlighted safety fears "within the trust's maternity services", Prof Baker said.
"This action is subject to a period of appeal and we will provide further information when the legal process allows."
A spokesman for SaTH said: "In line with normal CQC processes, we will be making representations to them in respect of this matter within the permitted 28 day timeframe."
'So many questions'
In 2013 Tasha Turner's first child Esmai was born by Caesarean section at 36 weeks at Royal Shrewsbury Hospital.
Ms Turner, 25, said she was assured there was no cause for concern and her daughter was soon drinking her breast milk with the aid of a tube. But when she went to check on Esmai the following morning, she was on life support.
Ms Turner said she was told Esmai had lactic acidosis, a build up of lactic acid in her body, and after four days Ms Turner and partner Jacob were advised to remove life support.
The couple said when they asked what led to their daughter's death they were told by the hospital "it happens".
The couple have since had two more children but said they are determined to know what happened to Esmai.
"I have so many questions," said Tasha.
"How was I told when she was born that she was fine, and then she dies four days later? I've looked up the condition she had - no way should it kill someone."
Deirdre Fowler, Director of Nursing, Midwifery and Quality at SaTH said: "We recognise that, taken in isolation, the number of cases which are being considered may cause concern or anxiety for families currently using our services.
"It is important that any families who have any questions or concerns over their care are given the chance to have them explored."