The FSA has confirmed it has today executed search warrants on the Castlestone Management's premises in London and Chichester, as a fourth member of staff leaves the group.
The regulator refused to comment further on the search, saying "The FSA's regulatory investigation is ongoing."
In a statement, Castlestone said: "Castlestone Management Limited can confirm its premises were visited by the FSA this morning as part of a regulatory investigation. The company is cooperating fully with that investigation. A further statement will be made as soon as possible."
Meanwhile Connor Noonan has become the fourth member of staff to leave Castlestone since May.
Noonan was a commodities analyst working on the $34.7m Aliquot Commodity (UCITS) fund which was one of three portfolios to have subscriptions suspended by the Central Bank of Ireland in May.
His role is being covered by other members of the investment team, the group said.
The other two funds affected by the suspension, which was lifted on 10 June, are the $19.64m Aliquot Agriculture (UCITS) and $4.23m Intelligent Portfolio (IQ) Asset Allocation (UCITS) funds.
CEO Angus Murray has become lead manager on the latter, as well as the Aliquot Commodity UCITS fund, while Robert Hunt is named manager on the commodity fund.
Noonan's resignation follows that of Bradley Yim, who ran one of the affected funds, and Arrash Zafari, who left the group in May, handing his Next 11 fund to Murray.
Yim is involved in a legal dispute with the firm, his lawyer said.
Head of compliance and legal Ed Williamson also left the group in this month after his role was split between two other staff.
At the time of the suspension, Castlestone released a statement saying the Irish regulator wanted a higher level of disclosure under UCITS IV, and had requested a new business plan from the firm for the transition to UCITS IV.
It said: "Additional documents have been requested to satisfy a change of administrator which Castlestone has implemented in its continued effort of trying to lower the TERs of the funds."
However, it later retracted this statement, issuing a second one after the suspension was lifted, in which the group said it "undertook to improve the reporting process and implement several other management changes including the approval of an enhanced UCITS IV business plan which was approved prior to the UCITS IV implementation deadline."
The group now says it did not take steps to reduce the TERs on the three funds, which have been capped at 5%, but instead brought currency hedging in house in order to lower costs.
Despite the funds' size and investments in relatively illiquid markets, Castlestone said it has no concerns about being able to meet redemptions.
"The instruments the funds trade are completely liquid and therefore the size of the AUM of the fund is irrelevant to Castlestone being able to meet redemptions," it said.
In fact, the group said between the three funds being suspended and shortly after the suspension was lifted, the portfolios saw net inflows equivalent to 5% of AUM.
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From 1 March