Washington ? The Obama administration warned insurance companies Monday they face possible legal action for allegedly trying to scare seniors with misleading information about the potential for lost benefits under health care legislation in Congress.

“As we continue our research into this issue, we are instructing you to immediately discontinue all such mailings to beneficiaries and to remove any related materials directed to Medicare enrollees from your Web sites,” said a notice from the Centers for Medicare and Medicaid.

In one case, the Health and Human Services Department, which oversees CMS, launched an investigation of Humana after getting a complaint from Sen. Max Baucus, D-Mont.

President Barack Obama’s health care legislation is moving toward key tests in a Senate committee over the next several days, and with public polls showing widespread skepticism among seniors.