Military liaison officer Shawn Green, a sergeant first class, was on a temporary posting to PNG to assist with security planning for the upcoming Asia Pacific Economic Cooperation (APEC) summit.
The US embassy said Green was found dead at a friend’s house in a secure compound where many US and other diplomats live at around 3am on April 27.
The 38-year-old’s body was flown to the US for an autopsy.
PNG police have expressed frustration at being excluded from the investigation, but the US embassy said the case was being dealt with properly.
“It’s a diplomatic case and is being handled according to international protocols,” US embassy spokeswoman Beverly Thacker said.
The US Army said Green was a decorated Special Forces weapons sergeant normally based in Okinawa, Japan.