A health watchdog has launched an investigation into an "unacceptable" £29.5 million deficit run up by an NHS hospital trust.
Monitor said the Heart of England Foundation Trust (HEFT), which runs three hospitals in Birmingham, Solihull and Sutton Coldfield alongside others services, had "slipped worryingly into the red".
Announcing an immediate investigation, the watchdog said it had concerns over the trust running such a large deficit so early into the financial year, and the decision to use its cash reserves to pay for day-to-day running.
The trust has accepted responsibility for its "difficult financial position" but said its problems were not exclusive to it, adding it had recently invested "heavily" in improving patient services.
Heart of England provides services for 1.2 million people across the area and has an annual budget of £650 million.
Monitor said, with the trust "heading for a significant deficit" by the financial year's end in April next year, it was launching an investigation to identify under-lying causes of the deficit and "what needs to be done to fix it".
Marianne Loynes, Monitor's regional director, said: "This trust has slipped worryingly into the red, using its cash reserves to prop up the day-to-day running.
"A deficit of £29.5 million in five months is simply not acceptable and we want to establish what can be done to ensure the trust continues to provide the services local patients value."
Dr Andrew Catto, the hospital trust's deputy chief executive and executive medical director, said: "This is a very serious situation and the trust already has plans in place which it believes will make a difference quickly.
"This is not an investigation into the quality of care that HEFT provides, it is part of a normal response when a trust is not performing as expected, and with the current financial problems across the NHS, is not unique to this trust.
He added: "The trust accepts responsibility for this difficult financial position, conscious decisions were made to invest heavily in making improvements for patients such as reducing the waiting times in A&E, ensuring shorter waiting times for operations and the recruitment of 160 new nurses.
"The welfare of our patients and staff is the most important thing and this will not be compromised."
The trust operates several services including running Birmingham Heartlands Hospital, Solihull Hospital and community services, Good Hope Hospital in Sutton Coldfield and Birmingham Chest Clinic.
An announcement on the investigation's outcome will be made in the next few weeks, according to Monitor.