The Pension Protection Fund (PPF) has looked into into whether cash was extracted from the Bernard Matthews pension scheme when the company went into administration.
Trustees of the scheme are also investigating the funding of the scheme, the Financial Times reports.
Both the trustees and the pensions lifeboat seek to maximise recoveries for 700 members of the scheme after the turkey producer entered administration last year.
Many members may see cuts to their retirement income as the plan is being absorbed into the PPF.
According to Antony Miller, chief executive of 2020 Trustees, the scheme's funding shortfall, which would have to be covered by the PPF, was now projected at £30-£40 million.
Miller told the Financial Times the trustees were looking into issues about the scheme's funding alongside the PPF.
'We are investigating whether actions taken in recent years were appropriate, necessary and resulted in the pension scheme receiving fair value,' he said.
'We are reviewing a vast amount of historic data and communications and will use the findings to conclude on what action, if any, that we should take and whether to involve the pensions regulator.
'It is clear in this case that our members have suffered and that certain other parties have gained.'
Bernard Matthews was sold under a pre-pack administration in September to Ranjit Boparan, owner of the 2 Sisters food group, a move which saved 2,000 jobs.
However, a report prepared for the Work and Pensions Select Committee by Prem Sikka, a professor of accounting at the University of Essex, described the administration as 'carefully crafted' to benefit secured creditors and company controllers to the detriment of the pension scheme.
The former private-equity owners of the turkey giant Rutland Partners stood to gain £39 million, while the pension scheme, which held a £17.5 million security, received no payment for the sale, according to the terms of the administration.
The PPF does not have investigatory or regulatory powers but said it was working to maximise recoveries for the lifeboat scheme.
A spokesperson for Boparan declined to comment.