London ? Lawmakers pledged today to study the movements of planes and ships traveling to the remote British outpost Diego Garcia amid persistent suspicion it is used by U.S. authorities to detain or transfer terrorism suspects.

Parliament’s Foreign Affairs Select Committee said it plans a thorough investigation of the use of the Indian Ocean island, which hosts a U.S. military base. Britain leased Diego Garcia, which is halfway between Africa and Southeast Asia, to the United States, and in 1971 barred anyone from entering the islands except by permit.

The United States initially denied using the island for extraordinary rendition flights. However, it acknowledged in February that it had misled the British government and that two suspects had been on flights that stopped to refuel on Diego Garcia en route to Guantanamo Bay and Morocco in 2002.