Dr. John Howard, the longtime head of NIOSH and a handful of teams at the agency had their layoff notices rescinded on May 13, multiple officials told news services, and several worker safety programs that had been eliminated by layoffs last month are being restored.

Letters reversing the layoffs arrived in the inboxes of some NIOSH staff a day ahead of House and Senate hearings May 14 with Health and Human Services Secretary Robert F. Kennedy Jr. where he faced questions about the layoffs.

Health officials and scientists being brought back to work include everyone in NIOSH's respiratory health division, division of safety research, division of compensation and analysis support and National Personal Protective Technology Laboratory according to an email obtained by CBS News.

"Secretary Kennedy has been working hard to ensure that the critical functions under NIOSH remain intact. The Trump Administration is committed to supporting coal miners and firefighters, and under the Secretary's leadership, NIOSH's essential services will continue as HHS streamlines its operations," HHS spokesperson Andrew Nixon said in an email.

A handful of NIOSH staff working in the agency's World Trade Center Health Program previously had their layoffs reversed, after a second round of cuts at the agency earlier this month. 

"While we celebrate with those who received a rescission letter from HHS, I am mindful that others did not. I am hopeful that we can continue to make the case for reinstating everyone at NIOSH," the agency's now-reinstated director, Dr. John Howard, wrote in the email.

The reinstatements mean that some NIOSH programs might soon resume.

The National Personal Protective Technology Laboratory had been forced to suspend new approvals of respirators after the initial round of cuts on April 1. Investigations of workplace health risks through NIOSH's Health Hazard Evaluation program were also suspended by the layoffs, but staff working in those probes have now been reinstated.

But many workers also remain effectively laid-off at the wide-ranging agency, according to news reports.

In NIOSH's Spokane and Pittsburgh Mining Research Division, laid-off scientists and engineers were called back to work, but only for a few more weeks to wind down their laboratories and research before their layoff notices take effect. Those NIOSH employees have not received letters formally rescinding their layoffs, unlike some of their colleagues.

Part of their work includes overseeing miner safety programs like the personal dust monitors, or PDM, required by the Department of Labor for coal miners. NIOSH is responsible for testing PDM's accuracy. The monitors are needed to reduce the risk of black lung disease. 

Other parts of the Centers for Disease Control and Prevention, which currently houses NIOSH, also remain off the job, despite calls from states and lawmakers for their reinstatements. HHS previously said it was planning on moving what remained of NIOSH into a new agency called the Administration for a Healthy America.