Authorities at Europe’s second largest port, Antwerp, said on Friday they closed a dock for traffic after detecting late on Thursday afternoon an oil spill that had occurred during a bunkering operation. The authorities are using drones to determine the extent of the oil leak and have already begun clean-up operations. A total of 20 ships have been found to have oil on them and they cannot leave the Deurganck Dock until they are cleaned from the oil, the port authorities said. Oil was also detected in the shipping…