CIA-released intelligence documents show the Taliban warned Osama bin Laden to tighten his security after the 1999 hijacking of Indian Airlines Flight IC-814, fearing the hostage crisis could be used to target him. The documents, part of 71 Presidential Daily Briefs released ahead of the 25th anniversary of 9/11, also reveal that US intelligence had tracked bin Ladens plans for attacks in India and other countries, his interest in acquiring chemical, biological and nuclear materials, and warnings about potential attacks on US soil.