Employees at Walgreens pharmacies across the U.S. walked out Monday, protesting what they call unsafe working conditions at the stores.

Closures were confirmed by CNN at Walgreens stores in Oregon, Washington, Massachusetts and Arizona.

Walgreens staff and pharmacists have reported understaffed teams having to meet increased demands, such as dealing with backlogged prescriptions and administering vaccines.

Employees are asking that the company hire more staff, be transparent about how payroll hours are assigned, create mandatory training hours and give advance notice when a position opens at a store or when staff will be reduced.

Walgreens spokesman Fraser Engerman said in a statement to the Washington Post that the past few years have been “unprecedented” and “a very challenging time.” Walgreens didn’t immediately respond to a request for comment from The Times.

“We also understand the immense pressures felt across the U.S. in retail pharmacy right now,” he said. “We are engaged and listening to the concerns raised by some of our team members. We are committed to ensuring that our entire pharmacy team has the support and resources necessary to continue to provide the best care to our patients while taking care of their own well-being.”

The walkout follows walkouts a few weeks ago by CVS pharmacy employees at locations in Kansas City.

The Times unveiled in an investigation last month that Californians were being harmed by errors at chain pharmacies such as Walgreens and CVS because pharmacists were overworked, having to fill hundreds of prescriptions during each shift while vaccinating patients, working at the cash register and calling doctors to confirm prescriptions.

Pharmacies in California will now have to report prescription errors under legislation recently signed by Gov. Gavin Newsom.

The bill, written by Assemblymember Matt Haney, a San Francisco Democrat, allows pharmacies to increase staffing when they believe the workload is too much to handle.