Two Army helicopters crashed Monday night in a training area at Joint Base Lewis-McChord (JBLM), killing all four aviators aboard.
The crash occurred sometime after 8 p.m. a JBLM statement said.
Two OH-58 Kiowa observation helicopters went down inside the southwest training area at JBLM, in Thurston County.
Names of the dead have not been released pending notification of next of kin.
There was no one else aboard the copters, and no injuries to anyone on the ground. The cause of the accident was not immediately known.
An investigation has already begun by local authorities at JBLM. The Combat Readiness Center at Fort Rucker, Ala., will lead the overall investigation into the accident, JBLM said.