U.S. regulators have opened a new line of inquiry in their mortgage foreclosure probe and are asking big Wall Street banks about the beginning stages of mortgage securitization, two sources familiar with the probe said.

The Securities and Exchange Commission launched the new phase of its investigation by sending out a fresh round of subpoenas last week to big banks including Bank of America Corp., Citigroup Inc., JPMorgan Chase & Co., Goldman Sachs Group Inc. and Wells Fargo & Co., the sources said. Get the full story »