New evidence of China’s spy balloon program has been uncovered by BBC Panorama. The evidence includes flights over Japan and Taiwan. Japan has confirmed balloons have flown over its territory and it says it is prepared to shoot them down in the future.

China has not directly addressed the evidence presented. US-China relations were strained earlier this year when an alleged Chinese spy balloon was shot down off the coast of the United States. China claimed the balloon was a civilian airship, used for scientific research, and that it was an isolated event. A former East Asia analyst for the CIA said that the incident had been a part of a continuing effort that started at least five years ago. BBC has worked with Synthetaic to sift through data captured by the satellites and has found multiple images of balloons crossing East Asia. A representative from the Japanese ministry of defense said that the government is taking all precautions to monitor the situation daily. The US State Department believes the balloons are equipped to gather signals intelligence.

Read More: New images show Chinese spy balloons over Asia