Four Democratic members of Congress have called for an investigation into whether Health and Human Services (HHS) Secretary Tom Price and his department have engaged in “covert propaganda” or illegal lobbying by producing videos criticizing the Affordable Care Act (ACA), which were distributed via official social media accounts.

In a letter sent this week to the Government Accountability Office (GAO), the congressional Democrats cited tweets from both Price’s account—@SecPriceMD—and the department’s official media account, @HHSMedia.

A sampling of tweets from Price include:

Under Obamacare, coverage ≠ care. Another broken promise…one that’s hitting Mollie’s #smallbiz & others like it. Time to #RepealAndReplace.

And:

#Obamacare = rising costs. Obamacare = broken promises. It has meant that Gina’s #smallbiz can’t afford coverage for her employees.

Some of the tweets featured short videos of people complaining about the ways they believe the ACA, or Obamacare, has negatively affected their lives. Other tweets or social media posts linked to news interviews with Price in which he criticized the ACA, and supported the Republican plan to replace it.

The four Democratic signatories of this week’s letter—Sens. Ron Wyden (OR) and Patty Murray (WA), and Reps. Richard Neal (MA) and Frank Pallone Jr. (NJ)—said that the alleged violations by Price and HHS should be seen in the context of the overall conduct of the department under the Trump administration’s control.

“We are especially concerned by these actions because they appear to continue a pattern of behavior by the Department of using federal resources to advance partisan legislation,” they wrote.

Federal law prohibits government departments from using taxpayer dollars to promote policies without making clear that those messages were produced by the government. The GAO in a 2015 decision pinged the Environmental Protection Agency (EPA) for similar conduct. The EPA had produced videos that supported proposed regulations through the Clean Water Act. The videos did not contain graphics or text that indicated that the EPA had produced them. Once the EPA circulated the videos online, they reached up to 1.8 million people who would not have had any way to know they were viewing government-produced content.

Another tweet from Price, which was retweeted by the official HHS Twitter account, linked to a video in which Price promoted the GOP’s American Health Care Act and asked “every single senator to engage” in drafting and passing a bill that would leave 23 million more people uninsured. In the 2015 decision, the GAO found that the EPA had violated the federal prohibition on using taxpayer funds for lobbying when it circulated social media posts that linked to widgets allowing people to contact members of Congress to voice support for the water regulations.

Government departments that violate these laws must note the amount of misused taxpayer dollars in filings under the Antideficiency Act, a federal law that prohibits unauthorized spending of appropriated funds.