The caption given to this photograph by B. B. Morton  may be erroneous.  "Pillbox" was a name given to many constructions on Corregidor, usually until the name could be discovered. (The maps were woefully inadequate.) For a while, Battery Wheeler was known as a "pillbox." Was this a photograph of Battery Wheeler, or something very close to it, exploding?

This image is one of a series taken from an MG platoon position at the top of the rise above the trolley line, overlooking Landing Field A. The photographer was on the grass verge near the roadway towards the western end of Topside. That makes it almost certain that the buildings in the mid distance of the photograph are the NCO's Married Quarters. Draw a line connecting the two points, and this places the source of the explosion near  Battery Wheeler.  It may well be the 161st blowing the portal of the Wheeler Tunnel.