Some former employees of the National Oceanic and Atmospheric Administration who were fired, rehired and fired again this spring say they have received debt notices from the federal government to pay it back for health care coverage. Those workers also say the notices are for coverage they never had.

The workers say it’s the latest development in a firing process mired in confusion, poor communication and missing paperwork as they confront the most basic workplace questions.

Three former NOAA employees shared letters titled “DEMAND NOTICE FOR PAYMENT” with NBC News. The letters, dated June 16, claimed the employees owed a debt — sometimes hundreds of dollars — and that interest could be charged. The letters also warned that the debt would be reported to a credit bureau if it went unpaid.

“It’s very gloomy and threatening language,” said Sarah Cooley, who was fired as the agency’s ocean acidification program director in late February.

It’s not clear exactly how many workers who were laid off received the letter. Two former NOAA employees told NBC News they did not receive any such letter.

The notice says the charge is for health care premiums for the eighth and ninth pay periods of the year, a time when their health coverage plans had already expired, the workers said.

“They’re trying to bill me for health insurance after I was fired. I had no coverage,” said Ya’el Seid-Green, a former special assistant in NOAA’s Office of Oceanic and Atmospheric Research. “It’s just more salt in the wound on how incompetent all of this has been.”

Kim Doster, a NOAA spokeswoman, said the agency could not comment on ongoing personnel matters and directed questions to the Office of Personnel Management. An OPM spokesperson said the agency did not have access to personnel or payroll records at other agencies, like NOAA. The Commerce Department, which oversees NOAA, did not respond.

After NBC News inquired about the problem with NOAA’s media affairs group, probationary employees received an acknowledgment of a possible error from the agency in an email.

“Our office has been made aware that you may have received a debt notice from the National Finance Center (NFC),” the email to probationary employees read. “Please know we are working with NFC to resolve this. No action is needed from you right now. We’ll keep you updated as we have more information.”

In February, the Commerce Department fired more than 600 probationary employees at NOAA, including hurricane hunters, meteorologists and storm modelers. Probationary workers are typically in the first or second year of a new position at the agency.

In mid-March, a judge ordered many workers to be reinstated and NOAA placed them on administrative leave. Then, in early April, the Supreme Court paused some of the reinstatements and NOAA fired the workers for a second time.