Images taken by digital imaging group DigitalGlobe on February 22 show an increase in activity at a facility in Sanumdong, a suburb of Pyongyang.
North Korea has already assembled some of its intercontinental ballistic missiles and the launch of satellites in Sanumdong.
Two experts interviewed by CNN stated that the activity provided for a satellite launch.
"In Sanumdong we see a lot of vehicle activity and also at the station where it should be loaded and brought to So," said Lewis, who studied the pictures. "I think the evidence points to a satellite launch, not only on Sanumdong, but also on the evidence from Sohae." [Lewis] warned that it was impossible to know whether the North Koreans were preparing a military rocket or a space rocket. It is also possible that the activity was a deliberate attempt to attract the attention of US spy satellites.
The US State Department declined to comment.
"Since this facility produces both ICBMs and space rockets, we do not know what's on the train, "said Melissa Hanham, North Korea's expert on the One Earth Future Foundation. "We do not know how far the train has come."
Hanham believes a satellite launch is the more likely scenario as there has never been an ICBM launch from Sohae. She also says that the activity at the launch site should indicate about a week in advance if a startup is imminent.
"There has never been a surprise start from Sohae," says Hanham.
Satellite launches use technology similar to ballistic missiles. Experts have long pointed out that North Korea's attempts to launch satellites into space could help them develop long-lasting ballistic missiles.
The North Korean missile program made progress in 2017, and Pyongyang said it has successfully fired three intercontinental ballistic missiles. Experts say the Hwasong-15, launched at the end of November, is likely to hit a large part of the United States.