Former President Jimmy Carter has criticized Israel's blockade during a trip to Gaza. He encouraged the territory's Hamas rulers to accept international conditions for ending its boycott of the militant Islamic group. During his visit, Hamas security found what appeared to be explosives buried in a sand dune next to Carter's route. No one was hurt, and it was unclear if the former president was being targeted. Carter spoke at a graduation for students from United Nations-run schools in Gaza City. He criticized the Gaza blockade imposed by Israel and Egypt after Hamas took control. Carter's Gaza visit came at the end of a swing though Lebanon, Syria and Israel. He encouraged officials in all countries to move toward a negotiated end to the Middle East conflict.