The state of Massachusetts has subpoenaed two investment banks about their research on US subprime lenders whose shares have plunged in recent weeks and Banc of America Securities paid a $26m (€19m) fine four years after Eliot Spitzer's campaign to stamp out conflicts of interest on Wall Street.

William Galvin, the state's secretary of the commonwealth, has asked Bear Stearns and UBS for documents about analyst recommendations of the subprime sector.