Japan’s Asahi Shimbun is reporting that North Korea may have developed a larger intercontinental ballistic missile (ICBM) of unknown range in its efforts to develop a rocket that can hit the US mainland. The story follows reports last month of satellite imagery showing that the North may have moved new ICBMs from a factory near Pyongyang for future testing.

The Japanese newspaper cited sources familiar with North Korean military affairs as saying that the suspected missile’s other capabilities are not clear. But they noted indications in late September that Pyongyang had completed an upgraded version of the Hwasong-14, an ICBM that it twice fired in July. The Hwasong-14 is a two-stage rocket believed to have a range of about 13,000 kilometers.

Japan, the US and South Korea have already raised their alert levels in anticipation that North Korea will conduct more missile tests.

A Russian lawmaker said last week that North Korea is preparing to test a long-range missile that it believes can reach the West Coast of the United States.