SUEZ, Egypt—Efforts to dislodge a giant container ship blocking the Suez Canal have allowed its stern and rudder to move, but it remains unclear when the vessel will be refloated, the head of the canal authority said on Saturday. The 400 metre (430 yard) long Ever Given became wedged diagonally across a southern section of the canal amid high winds early on Tuesday, blocking one of the world’s busiest waterways. A combination of dredging material from around the ship and pulling and pushing the vessel with tugboats made minor progress in dislodging the ship on Saturday, two SCA sources said. One source said there had been some movement at the bow of the ship. Suez Canal Authority (SCA) Chairman Osama Rabie told local TV that water had started running underneath the ship. “We expect that at any time the ship could slide and move from the spot it is in,” he told a …