A federal inspector general has launched an inquiry into the Trump administration's decision to pull advertising for HealthCare.gov in the closing stretch of this year's sign-up season, according to a letter made public Friday.

The unexpected ad pullback soon after President Donald Trump took office was termed "sabotage" by Democrats and former Obama officials. The new administration said the ads were a waste of taxpayer dollars.

In a letter to Democratic Sens. Patty Murray of Washington and Elizabeth Warren of Massachusetts, the Health and Human Services Department's inspector general's office said it has begun a "fact-finding review."

Investigators will look at the Trump administration's actions to stop paid advertising and temporarily suspend other outreach. They'll also review the effect on enrollment, the letter said.

Former Obama officials were outraged by the new administration's actions a few days before the Jan. 31 close of open enrollment. They said there's usually a surge at the end sign-up season, and the ad pullback discouraged prospective customers. Murray and Warren asked the inspector general to investigate.

About 12.2 million people have signed up for coverage this year through HealthCare.gov and state insurance markets, short of earlier Obama administration projections.

In a statement, Murray said HHS has "a duty to provide the public with accurate and timely information so that they can make decisions about their health care."

There was no initial response from the Trump administration.