Activity at a North Korean nuclear testing site picked up late last month, according to an analysis of satellite imagery, after a brief lull. But those photos also show activity of an entirely different sort: volleyball.

The analysis, compiled by Joseph S. Bermudez Jr. and Jack Liu on the website 38 North, focuses on commercial satellite photos from the Punggye-ri Nuclear Test Facility in the northwest part of the country on April 25. The website analyzes information for North Korea watchers and is a program under the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies.

(Photos courtesy: Airbus Defense & Space and 38 North. Includes material Pleiades © CNES 2017 Distribution Airbus DS / Spot Image, all rights reserved.)

The photos were taken a day before all 100 U.S. senators received a classified briefing on the White House grounds over the North Korean nuclear threat, and before Pacific Command chief Adm. Harry Harris testified in front of Congress on the same issue. A day earlier, the guided-missile submarine USS Michigan appeared in the South Korean port city of Busan, considered a further massing of forces beyond the imminent arrival of the Carl Vinson Carrier Strike Group.

The authors refer to an "apparent resumption of activity" at the site after a break, specifically the pumping out of water from a tunnel the North Koreans plan to use to test a nuclear weapon, something they have been doing for several weeks.

"Several probable mining carts appear to be present, although there does not seem to have been any significant dumping of new material on the spoil pile. The netting canopy previously sighted over probable equipment near the North Portal's support building remains in place, but no vehicles or personnel are readily visible in the area," Bermudez and Liu write.

Another photo shows the northern and southern courtyards, where "personnel are possibly engaged in a volleyball game." And in the courtyard of the Command Center Area and the Guard Barracks, more volleyball games appear to be underway.

The authors say the imagery alone doesn't indicate whether a nuclear test "has been cancelled, the facility is in stand-by mode or that a test is imminent." They add that the placement of people could be a reaction to media coverage of 38 North's previous reports of volleyball games.

"The presence of a large number of people dispersed throughout the facility in the latest image, however, is unusual and almost assuredly a component of an overall North Korean deception and propaganda effort and the result of international media reporting on 38 North's sightings of volleyball courts and games in progress on April 19 and 21."