The Serious Fraud Office has launched a wide-ranging investigation into the sale of storage "pods" which has put over £120m of investors' money at risk.
Several pension schemes, including the Capita Oak Pension and Henley Retirement Benefit plans, and self-invested personal pensions (Sipps) are being investigated as part of the probe which covers investments made since 2011.
The alleged fraud involves purchasing self-storage containers and then renting them out.
Over a thousand people are believed to have been affected, most of them holding the investments in their pensions. The sums invested total over £120m, said the SFO.
The Westminster Pension Scheme and Trafalgar Multi Asset Fund are also being investigated in relation to other types of investments.
Pension reforms have led to savers leaving money invested after retirement and a boom in the number of new Sipps which allow a greater range of investments than workplace or traditional personal pensions.
Kate Smith, of Aegon, the pension company, said the thousand investors identified by the SFO could be the "tip of the iceberg".
She said: "[This] is a timely reminder that unregulated unusual investments at home or aboard come with a high risk that people could lose all their hard-earned pension and other savings. Savers must be on their guard.
"Promises of high returns or financial inducements are often scams and people falling for this type of investment scam run the risk of their lifetime’s savings being lost in a matter of seconds."
The SFO would not comment further but urged anyone who may have invested through the schemes to fill out a questionnaire.
The investigation is being conducted in conjunction with "Project Bloom", a multi-agency taskforce set up to highlight pension scams. Losses from pension scams hit a monthly record high of £8m in March, according to City of London Police figures.
Following pressure from this newspaper the Government said it would make it illegal to make cold calls about pensions and investments. But the measure was delayed as the Finance Bill was trimmed to ensure it passed before the snap general election.
Andrew Tully, of pension firm Retirement Advantage, said: "Pension freedoms are providing more choice for savers but have also opened up the market to conmen and fraudsters who prey on the vulnerable and those hoping for early access to their pensions.
"The sooner we can get this legislation back on the next government’s agenda the better."