Blog 38 North, edited by a North Korea research team at the Maryland university, said its assessment of satellite imagery of a launch station indicated a rocket engine was tested there in late March or early April. North Korea conducted two long-range rocket launches from the same facility last year.
North Korean rocket programs put the western United States coast within reach. Rocket launches in 2006, 2009 and 2013 coincided with nuclear tests in North Korea.
Johns Hopkins researchers said it's unclear how many or what type of engines were tested at the Sohae Satellite Launching Station. They said it could indicate a test of a possible space-launch vehicle or for a rocket meant to carry a heavy satellite into orbit.
"The recent engine test indicates that Pyongyang continues to move forward with its space-launch vehicle and long-range missile programs despite continuing United Nations sanctions and China's public expressions of displeasure with the North's efforts to further develop nuclear weapons and the missiles to deliver them," the research team said Wednesday.
John Hopkins last month said it believed new operations were under way at the Punggye-ri nuclear test site. The site is where North Korea conducted tests in 2009 and 2013.