Water leak in my office

On returning to work after the extended weekend (i.e., last Friday, Veterans Day, was a holiday), I found that water had leaked into my office. The ceiling tile along the wall to an adjoining office was stained and still damp.



I then checked the adjoining office and found one ceiling tile so wet that it was bowed downward in the center.



It had not rained over the weekend. When I left work for the day, the source of the water was still unknown.

Update: Tuesday, November 15: The source of the water is believed to have been from a clogged overflow pipe for an air handler in the penthouse above the offices.