New Delhi, Oct. 27 -- Newly released Pentagon documents describe a reported encounter between federal agents and a large, black triangular object that climbed vertically, hovered in complete silence and accelerated away at speeds compared with those of a military fighter jet.

The incident took place in June near an unidentified national security site in the western United States. According to accounts included in the latest release of UFOs, or UAP, unidentified anomalous phenomena, the object had no visible exhaust, maintained a consistent thermal signature under infrared observation and disappeared from view within seconds of accelerating.

The US Department of Defense released 28 PDF files in its latest disclosure, the seventh batch re...