Japan has detected radio signals suggesting North Korea may be preparing for another ballistic missile launch, Reuters reported, citing a Japanese government source. However, such signals are not unusual and satellite images have not shown fresh activity, the source said on Tuesday. “This is not enough to determine” if a launch is imminent, according to the source. Kyodo reported late on Monday that the Japanese government was on alert after detecting radio signals that suggested a launch could come in a few days. The signals may also be related to winter military training by the North Korean military.