Foreclosure-fraud class action lawsuits are starting to pile up against major banks across the country, threatening a besieged industry with billions more in potential losses.

Bank executives are swarming Capitol Hill this week to defend themselves against multiple foreclosure-related investigations, including one by all 50 state attorneys general. Talks are under way in that probe in hopes of reaching a settlement, but that wouldn't extinguish the mounting threat of an avalanche of class actions.

A congressional watchdog said in a report issued Tuesday that the foreclosure document debacle could threaten major banks with billions of dollars in losses, further prolong the housing depression and damage the government's effort to keep people in their homes.

The class actions, which could be expanded nationally, seek damages for homeowners whose properties were illegally foreclosed upon by banks using fraudulent documents. Suits have been filed in Maryland, New Jersey and Massachusetts that target Bank of America Corp., Wells Fargo & Co., HSBC PLC and JPMorgan Chase & Co. In Florida and Maine, Ally Financial, formerly known as GMAC Mortgage, is also being targeted.