Within hours of the burglars' arrests, the FBI discovered E. Howard Hunt's name in Barker and Martínez's address books. Nixon administration officials were concerned because Hunt and Liddy were also involved in a separate secret activity known as the "White House Plumbers", which was established to stop security "leaks" and investigate other sensitive security matters. Dean later testified that top Nixon aide John Ehrlichman ordered him to "" the contents of Howard Hunt's White House safe. Ehrlichman subsequently denied this. In the end, Dean and the FBI's Acting Director L. Patrick Gray (in separate operations) destroyed the evidence from Hunt's safe.