Democratic senators are questioning the Trump administration about whether it has been doing enough to protect federal workers during the coronavirus pandemic. In a letter sent Monday to the White House, the senators demanded more information about the administration’s policies, and they cited ProPublica coverage detailing how agencies have come up short.

The administration has the “authority and responsibility to make sure that federal agencies have effective and clear policies to protect these employees,” wrote Sens. Elizabeth Warren, D-Mass., Bernie Sanders, I-Vt., and 20 other lawmakers.

Among the issues raised by the senators was the Postal Service’s apparent failure to tell employees whether they’ve been exposed to the coronavirus. As ProPublica has reported, many workers say they weren’t notified about sick colleagues despite the Postal Service’s promise to do so.

The letter — sent to the White House’s Office of Management and Budget as well as the Office of Personnel Management — took the administration to task for not moving more quickly to allow federal employees to work from home: The government “risked the safety of federal employees by waiting so long to issue strong telework guidance.” As the letter notes, the Department of Veterans Affairs barred administrative employees from working from home, a policy that was reversed a day after ProPublica and New Mexico In Depth reported it.

The senators said agencies are still not consistently following through on the policies allowing employees to work from home: “Almost one month after it was put in place, this guidance has still not led to a uniform or rapid shift to telework across all agencies.”

A spokesperson for the VA said that the agency is maximizing telework when possible and that its safety practices “have helped limit Veterans Health Administration COVID-19 employee infection rates to less than 1% of the workforce.” A Postal Service spokesperson did not immediately respond to requests for comment.

The letter raised concerns not just about the administration’s record of protecting federal employees, but also what the plan is going forward. The White House issued a memo last week encouraging federal agencies to allow employees back to the office in low-risk areas.

“Public health experts have expressed serious concerns about these guidelines and warned that there is still not sufficient testing, tracing, or personal protective equipment to know what, where, and when it is safe to relax certain social distancing and quarantine guidelines,” the senators wrote.

A spokesperson with the Office of Management and Budget responded in a statement: “Agencies have been given clear and consistent guidance throughout this crisis to maximize telework, and they are now working to return to normal operations as conditions warrant across each state.”

The White House’s guidance directs agencies to use a series of benchmarks based on coronavirus decline and medical preparedness in their offices’ locations to decide when to return operations to normal. Agency leaders, it says, must “provide federal government leadership and momentum as an impetus toward a broader national return to normalcy.”

The senators asked the administration to answer 12 questions about its implementation of telework and other safety protocols across federal agencies. They asked for a response by May 11.