North Korea is said to be on the verge of another nuclear test

Kim Ju-sung/Yonhap via REUTERS

A South Korean soldier watches a TV broadcasting a news report on Seismic activity produced by a suspected North Korean nuclear test, at a railway station in Seoul, South Korea, September 9, 2016.

US officials say North Korea's sixth nuclear test could come as early as Saturday morning.

Officials and other sources said the reclusive nation had placed a nuclear device in a tunnel, which could be detonated by the end of the week, a ccording to Steve Herman, White House bureau chief of Voice of America News.

The suspicion is also corroborated by four weeks of "high levels of activity" at the Punggye-ri nuclear-test site, according to 38 North, a research group from the US-Korea Institute at Johns Hopkins University.

The research group's findings included new commercial-satellite imagery that showed the location of the tunnel, where four of North Korea's recent nuclear tests were also initiated, in addition to other evidence of an imminent test.

According to their analysis, water being pumped from the suspected tunnel was being soaked to the ground elsewhere, which may indicate that the tunnel was being prepped for testing devices. Additionally, tracks from footsteps and vehicles were visible from the melting snow. Identifying the exact equipment being used proved to be difficult, however, due to what appeared to be netting that covered the area.

"We have no comment at this time but we will be watching closely," a defense official said to VOA.

Here's the satellite imagery taken by Airbus Defense & Space and 38 North on April 2: