PARIS — A senior Dutch government official’s disclosure that one victim of the Malaysia Airlines plane crash in eastern Ukraine had been found wearing an oxygen mask led to dismay on Thursday among investigators and outrage among victims’ relatives.

“People are shocked when they hear this and wonder what other information there is but isn’t shared,” Veeru Mewa, a lawyer representing the families of several Dutch passengers who died aboard the plane, told Dutch television.

Frans Timmermans, the foreign minister, mentioned the discovery of the oxygen mask late Wednesday during an appearance on a popular Dutch television talk show, where an interviewer brought up the July 17 crash of Malaysia Airlines Flight 17, which killed 298 people.