Chagai-I is the code name of five simultaneous underground nuclear tests conducted by Pakistan at 15:15 hrs PST on 28 May 1998. The tests were performed at Ras Koh Hills in the Chagai District of Balochistan Province.Chagai-I was Pakistan's first public test of nuclear weapons. Its timing was a direct response to India's second nuclear tests, on 11 and 13 May 1998.