32 CFR 553.15: Eligibility for group burial in Arlington National Cemetery.

(a) The Executive Director may authorize a group burial in Arlington National Cemetery whenever several people, at least one of whom is an active duty service member, die during a military-related activity and not all remains can be individually identified.

(b) Before authorizing a group burial that includes both United States and foreign decedents, the Executive Director will notify the Department of State and request that the Department of State notify the appropriate foreign embassy.