Washington (CNN) Republicans and Democrats on the Senate Veterans Affairs Committee are raising concerns about allegations involving Rear Adm. Ronny Jackson, President Donald Trump's nominee to lead the Department of Veterans Affairs, and are reviewing them to determine if they are substantial enough to upend his nomination.

Committee members have been told about allegations related to improper conduct in various stages of his career, two sources said.

The sources say the committee is in talks to delay Wednesday's confirmation hearing as they try to figure out the allegations.

None of the senators would publicly detail the specifics of the allegations. A White House spokesman did not immediately respond to a request for comment.

Two Republican sources with direct knowledge of the situation say the White House is aware that both Democratic and Republican lawmakers are looking into potential problems. Republican lawmakers and aides on the committee say they are also grappling with the allegations, trying to assess what they mean for Jackson's nomination to the post.

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