A drone that apparently flew undetected over several NATO countries all the way from the Ukrainian war zone crashed overnight on the outskirts of the Croatian capital, Zagreb, triggering a loud blast but causing no injuries, Croatian authorities said Friday. A statement issued by Croatia's government said the “pilotless military aircraft” entered Croatian airspace from neighboring Hungary at a speed of 700 kph (430 mph) and an altitude of 1,300 meters (4,300 feet). The government said that an official criminal investigation will be launched and that NATO will be informed about the incident. The crash means that the large drone flew for at least 350 miles (560 kilometers) apparently undetected by air defenses in Croatia, Hungary and possibly Romania, all members of the Western military alliance. Military experts of The War Zone online magazine said that the aircraft is likely a Soviet-era Tu-141 “Strizh” reconnaissance drone that must have severely malfunctioned. It said that Ukraine is the only known current operator of the Tu-141.