Dozens of exhausted nuclear workers at the defunct Chernobyl nuclear plant, who have been working for three weeks straight ever since it was taken over by Russian forces, have been allowed to rotate out and make way for fresh workers, plant workers said in a Facebook post Sunday.

Staff at the plant, which includes more than 200 technical personnel and guards, had not been able to rotate shifts since February 23, a day before Russian forces took control of the site, according to the International Atomic Energy Agency, the nuclear watchdog of the United Nations.

But on Sunday, after about 600 hours inside, 64 people were allowed to leave, the plant said in a post on Facebook, where it has been delivering periodic updates on the perilous situation. Fifty shift workers were among those allowed to go, the plant said, and they were replaced by 46 “employee-volunteers.” It is unclear when or whether the remaining workers will be able to rotate out.

The facility’s employees have “heroically performed their professional duties and maintained the appropriate level of safety,” the plant’s post said.

For weeks, the IAEA has expressed concern for the workers at the Chernobyl site, calling for the staff to be rotated for their safety and security.

Rafael Mariano Grossi, director general of the I.A.E.A., said on Sunday that the workers “deserve our full respect and admiration for having worked in these extremely difficult circumstances.”

“They were there for far too long,” he said. “I sincerely hope that remaining staff from this shift can also rotate soon.”

Workers at the site have faced a number of issues recently, including a power outage and limited communication. Ukrainian government officials said on March 9 that damage by Russian forces had disconnected the plant from outside electricity, alarming those who feared it would disrupt the cooling of on-site nuclear material and potentially lead to radiation leaks.

While the plant’s Unit Four reactor exploded in 1986, showering much of Europe, Belarus and Russia in fallout, its remaining three reactors functioned for years afterward, with the last one closing in 2000.

After five days, during which time the plant used a backup generator for its electricity, engineers restored power, the IAEA said.