Who started the Watergate investigation?

March 1, 1974, a grand jury in Washington, D. C., indicted several former aides of Nixon, who became known as the "Watergate Seven"-H. R. Haldeman, John Ehrlichman, John N. Mitchell, Charles Colson, Gordon C. Strachan, Robert Mardian, and Kenneth Parkinson-for conspiring to hinder the Watergate investigation