Sen. Claire McCaskill, D-Mo., had strong words for Department of Veterans Affairs Secretary Robert McDonald on Thursday regarding the VA's failure to compensate thousands of World War II veterans who were exposed to mustard gas.

McCaskill has been requesting information from the agency ever since NPR reported the VA's mishandling of disability benefits for the veterans, some of whom are now in their late 80s and early 90s, and still waiting.

McCaskill said the VA has "blown past deadlines for briefings and documents" and "shown no urgency in addressing 70 years of appalling mistreatment of these men, many of whom have already passed away."

In a statement to NPR, the VA says it is conducting "extensive research to collect and validate the data and information Senator McCaskill has requested. VA is also looking to conduct additional outreach to any veterans newly identified as a result of this research."

Last summer, NPR revealed that despite promises made in the early 1990s, the VA failed to contact more than 3,000 veterans who were exposed to large amounts of mustard gas in secret military experiments and that the agency denied the veterans compensation based on a lack of documentation, even though such documentation was not available to them.

Since the report was published, more than two dozen members of Congress have written to McDonald demanding an explanation for the failures and calling for the swift disbursement of benefits for veterans who are still living.

In her letter Thursday, McCaskill wrote: "I am trying to help the remaining veterans before time runs out. This makes the VA's refusal to provide answers in a timely fashion all the more unacceptable."

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