The anti-aircraft missile that allegedly shot down a US F-15 fighter jet over southwestern Iran last month was most likely of Chinese origin, according to information reported by NBC, citing three sources with direct knowledge of the matter.

According to the network, one of those sources, as well as a US official, said China may also have supplied Iran with stealth aircraft technology and long-range early-warning radar equipment during the early stages of the war launched by Israel and the United States on February 28.

The same sources noted that the incident involving the downing of the US fighter jet remains under investigation. The episode had triggered an extensive 36-hour search-and-rescue operation to locate the aircraft’s pilot.

NBC said US authorities are continuing to examine the available evidence in order to determine the exact type of missile used, as well as the extent of any possible Chinese involvement in equipping the Iranian armed forces.

Last month, Donald Trump said he had asked Chinese President Xi Jinping not to supply Iran with weapons systems. According to Trump, the Chinese leader assured him at the time that, “basically,” he was not doing so.