A probe has been launched into emergency care provided by an NHS trust already at the centre of a storm over the deaths of newborn babies.
Detectives stepped in after a number of infants - reportedly at least seven - died at Furness General Hospital in Barrow, Cumbria, which is part of University Hospitals of Morecambe Bay NHS Foundation Trust.
The Care Quality Commission (CQC), which conducted its own examination of the maternity ward, has launched a wider investigation of emergency services across the trust.
It is only the third time the regulator has used its investigative powers since it came into being last April.
The decision follows an unannounced inspection last month which identified issues of "significant" concern in A&E.
It is understood some of these relate to "near misses" similar to those picked up in the earlier review of maternity services.
The investigation, which is expected to last eight weeks, will consider whether there are fundamental problems with the trust's procedures.
Debbie Westhead, of the CQC, said patients should continue to use accident and emergency services.
"If we felt there were immediate threats to the safety of patients, we would take immediate action," she said.
"This investigation will allow us to take an in-depth look at the care patients receive as they enter the hospitals for emergency care and at what happens to them subsequently.
"It aims to help the trust make sure it is providing sustainable good quality care. It should reassure local people that we are aware of problems in the trust and seeking more information to help the trust take the correct action to mitigate risks to patients."
The CQC will work with Monitor, the NHS foundation trust regulator, to ensure findings are addressed with appropriate regulatory action where required.
The trust was criticised by the CQC after inspectors carried out surprise inspections at Furness General Hospital's maternity ward in June.
Their intervention came the same month an inquest found midwives had repeatedly missed opportunities to spot and treat a serious infection before nine-day-old Joshua Titcombe, of Dalton, Cumbria, died at the hospital in October 2008.
The CQC report pointed out a failure to improve standards on the labour ward and highlighted six areas of concern in care provision.
Among them were the safety and welfare of patients, the suitability of maternity facilities and the degree to which staff worked together.
The trust - which consists of hospitals in Barrow, Morecambe, Lancaster and Kendal - has also come under fire from one of its own consultants who told a local newspaper that clinical staff had no respect for "a lame duck management".
The whistleblower claimed more than 30,000 patients had been affected with possible delays in treatment of more than a year in some cases.