The ambulance service has launched a fresh investigation into the sudden deaths of three of its staff.
Ambulance dispatcher Luke Wright, 24, and paramedics Christopher Gill and Richard Grimes all died within 11 days of each other in November last year.
A month earlier a whistleblower at the East of England Ambulance Service Trust (EEAST) had warned that a "toxic culture" was increasing the risk of suicide.
And in March 2019 staff in Norfolk told their bosses they were being "worked to the bone", leading to an increase in mental health problems.
After the deaths, the EEAST said it was doing everything it could to support staff, but three sources told this newspaper that the Trust's HR department, which included a wellbeing team, had been cut.
The Trust has now said it has launched an independent investigation into the "underlying factors associated" with the deaths.
Chief executive Dorothy Hosein said: "Our commitment to our people is to provide optimal wellbeing and welfare support. We are continuously reviewing and improving this and recently enhanced our provision.
"We regularly undertake extensive engagement and listening exercises with our staff to address their issues.
"We have significantly improved the way in which we listen and ensure that when they raise concerns with leaders within the Trust these are acted upon."
The evidence from the new investigation will be reviewed by a panel of experts and be completed by the end of February, but will not be made public, the Health Service Journal reported.
Speaking to the HSJ, the whistleblower who raised concerns in October, former equalities lead Paul Fitzgerald, claimed six EEAST staff had contacted him in recent months about mental health issues.
The new probe comes after a separate investigation by HR consultant Martin Tiplady into whistleblower concerns, which did not cover the sudden deaths.
The terms of reference of his investigation, completed this month, said its focus was on specific allegations but it would also comment on any systemic issues in the Trust.
Mr Fitzgerald said: "The only way to really try and sort the trust out is to hold a public inquiry."
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