The Mi-8 commercial helicopter downed in Iraq on Thursday was owned by Bulgarian air carrier Heli Air and worked on a wet leasing contract for a US company, according to the Bulgarian Transport Ministry.
The plane was leased by Washington-based Canadian SkyLink Air that is contracted by the US Defense Department.
The three-member Bulgarian crew of the copter and six civilian passengers, whose nationality is still not clear, died when the planed was downed by ground fire some 20km north of Baghdad.
The Balkan country has lost seven soldiers in bomb attacks and shootouts with insurgents in Iraq. An eighth soldier was killed last March by US troops in a friendly-fire incident.