A person familiar with the matter has disclosed the focus of New York attorney general Eric Schneiderman's investigation is to turn to the three banks.
As well as the trio of lenders, the insider - who cannot be named because the probe is not public - revealed four bond insurers have also been subpoenaed.
These are Assured Guaranty, Ambac Financial Group, Syncora Holdings and MBIA.
Mr Schneiderman is looking for information regarding claims that were paid out during and after the economic downturn, as well as documents concerning settlements or litigation with the banks, the source added.
It had already been reported that Mr Schneiderman was to correspond with major lenders Goldman Sachs Group, Bank of America and Morgan Stanley as part of the probe, which is being held alongside a nationwide investigation into the matter involving both state and federal regulators.
By Gary Cooper