Anglo Irish Bank's former chief executive David Drumm, who is living in Cape Cod in the US, has written to the garda fraud squad indicating he may agree to be interviewed by detectives probing financial irregularities at the bank.

Fraud squad detectives received direct correspondence from Drumm in the past few days, having written to him the week before stating they wanted to interview him as part of their investigation. A senior garda source said Drumm's letter was "not a substantive response" but added: "He gave no firm commitments but it was a step in the right direction."

Detectives sent similar correspondence to Anglo's former head of finance. Matt Moran, who is living in Luxembourg, but he has not responded yet.

The fraud squad cannot force either man to agree to be interviewed. Extradition proceedings can be used only for the purpose of charging someone with a criminal offence, not to compel them to return to Ireland to be questioned. But detectives are "quietly confident" that Drumm and Moran will agree to some level of co-operation.

"These were very senior people in the bank. There is simply no way they can ignore us," added the source. One issue gardaí want to discuss with both men is the transfer of €7.5bn from Irish Life & Perm­anent which bolstered Anglo's balance sheet on the last day of its financial year in 2008.

The Sunday Tribune has also learned that detectives are considering sending a file to the DPP in relation to possible criminality at Anglo in several parts rather than one extensive file.