The Secretary of Veteran's Affairs is under fire for hospital system failures that may have turned deadly, and may have been covered up.
The House Veterans Affairs Committee has subpoenaed emails and correspondence from top VA officials.
Allegations of backlogs and cover-ups have now spread from Phoenix, where 40 patients died while waiting for treatment to as many as five other states, including California, Colorado, Georgia, Texas and Wyoming.
Secretary Eric Shinseki is expected to testify before the Senate Veterans Affairs Committee on Thursday.
He is ignoring his critics' calls to step down, saying he serves at the pleasure of the President.