The victims suffered irritation to their eyes shortly before 6am local time (11am GMT).
They are believed to be security officials working for the Transportation Security Administration.
They were injured after inspecting a bag which set off an alarm during security check-in.
Three people have been hurt at LaGuardia Airport in New York
The New York Fire Department have been called to the scene and are investigating the substance.
The material has only been described as a "hazardous powder".
Emergency services at LaGuardia this morning
The airport is yet to comment other than to advise passengers to allow extra time.
LaGuardia is a major airport in Queens, New York, which serves almost 30 million passengers every year.
The area was temporarily closed but has since re-opened.