At least 22 "possible serious untoward" incidents - three involving deaths - have been recorded in connection with the new NHS 111 advice line, it has been reported.
Two deaths are being investigated in the East Midlands, and one in the West Midlands, health magazine Pulse said.
A spokesman from Derbyshire Health United - which covers NHS 111 in Derbyshire, Nottinghamshire and Northamptonshire - said it was investigating the two deaths but so far it believes the system and processes that were followed would have been "exactly as expected".
NHS Direct - which covers eight NHS 111 areas - said it is investigating the unexpected death of a patient who was referred to a GP out-of-hours service in the West Midlands, Pulse reported
NHS England's board members have voted to set up a review into the service
More top news
Hundreds remain missing in what is becoming one of the worst natural disasters to hit Central America in recent years.
Medical charity worker relates how he and colleagues tried to save patients and staff following devastating air strike.
Union leaders and officials from a range of campaign groups will address demonstrators as Conservative party conference gets under way.