North Korea conducted another rocket engine test on Wednesday which could potentially be used on a future intercontinental ballistic missile (ICBM), two U.S. officials told Fox News on Thursday. The test marks the first rocket engine test since the North Korean regime conducted three in March, which, in addition to an ICBM could also be used for a future new rocket capable of putting a satellite into orbit, according to both officials. The rocket test was conducted in the city of Yun Song, where previous rocket tests have taken place, one official said. The news of another rocket engine test out of North Korea comes as another U.S. official said Wednesday there are signs of increased activity at North Korea’s lone nuclear test site. “There are more people and more cars but nobody knows what that means,” said the official. North Korea has continuously carried out nuclear tests and ballistic missile tests in violation of UN resolutions. It has conducted five nuclear tests since 2006, including two last year. North Korea has declared that it could test-launch an ICBM “at any time” from any location set by its leader, Kim Jong Un, though it remains unclear whether any of its recent tests have been of an ICBM. U.S. officials told CNN Tuesday that if a sixth nuclear test by North Korea were to occur, it would be clear that the existing pressure by China on North Korea is not working. However, other senior officials said the administration's policy hinges on pressuring North Korea through China .