Dozens of officials in the U.S. Agency for International Development’s humanitarian aid bureau received termination notices over the weekend, despite prior assurances from Secretary of State Marco Rubio that the agency’s “core lifesaving medicine, medical services, food, shelter and substance assistance” would be preserved.

Beginning late Friday night, several now-former employees at the Bureau of Humanitarian Assistance received termination letters from personnel officers at USAID, according to copies of those letters obtained by ABC News.

BHA is the government’s lead federal agency for international emergency disaster relief, working closely with the military to provide humanitarian aid in the wake of earthquakes, typhoons, hurricanes and other global natural disasters.

Serena Simeoli, a Humanitarian Aid Adviser to the Military at BHA, told ABC News that she received a termination letter on Friday night, but that it was not addressed to her and did not include her name or contract number — so she remains “confused” about what to do.

Simeoli said her small team of some 60 employees had assisted during “sudden-onset disasters, complex emergencies,” including the earthquakes in Haiti and Syria, typhoons in the Philippines, hurricanes in the Caribbean, and the conflicts in the Middle East and Ukraine.

Without BHA, “it is going to be very challenging” for the U.S. to play a meaningful role in global emergency relief, “and I think I’m a little scared to think how it might go without us,” Simeoli said.

“The work that we do it matters, and we won’t know how much it matters until we’re presented with another catastrophic disaster,” she warned.

“I’ve devoted so much of my life to this organization … I would work around the clock because I believed in what we were doing,” Simeoli said. “It’s pretty painful to see and to be a part of what’s been happening.”

Another former BHA official said some colleagues reported receiving multiple termination notices, including some during the overnight hours this weekend.

That official, a former Marine, said that during his tenure with USAID he had responded to some of the world’s most challenging natural disasters .

“It makes me seriously question why I dedicated my entire adult life to carrying water in the most dangerous places in the world for our government and its people,” said the person, who asked not to be identified out of fear of retaliation.

Rubio wrote in a late January memo that he would grant an emergency waiver to allow USAID’s humanitarian missions to continue — but noted that the “resumption is temporary in nature.”

A State Department representative did not immediately respond to a request for comment from ABC News.