Traffic on the Suez Canal was moving freely again after a cargo ship, which drifted off course, blocked the vital waterway for several hours, a canal authority official said on Monday. Traffic resumed normally in both directions on Sunday evening after a four-hour interruption when a Hong Kong-flagged vessel drifted from its path, blocking the western channel, the official said. The ropes anchoring the 40,000 ton ship ripped, causing it to drift and blocking three vessels behind it. Tugboats were sent to pull the ship free and ease the congestion in the canal, the official said. The Suez Canal, which links the Red Sea and Mediterranean, is the third source of foreign currency for Egypt after tourism and remittances from overseas workers.