A naval search operation resumed at first light to find an estimated 100 people missing after a Tanzanian ferry sank near the island of Zanzibar.The boat had left the city of Dar es Salaam on mainland Tanzania on Wednesday with 290 people on board.So far 31 bodies have been recovered and more than 150 people rescued.Zanzibar’s police spokesman told the AFP news agency he feared there was now little hope of finding survivors from the MV Skagit ferry."Search operations continue but it is now almost impossible survivors will be found,” the agency quotes him as saying.Three days of mourning Survivors said they fear some of the passengers became trapped in vessel when it capsized in strong winds.Ali Mohamed Shein, president of the semi-autonomous archipelago of Zanzibar, has declared three days of national mourning.The ferry left Dar es Salaam at 12:00 local time (09:00 GMT) on Wednesday bound for the main island of Zanzibar.Hamza Kabelwa, director of the Tanzania Meteorological Agency, told the BBC’s Swahili service that a warning had been issued for vessels not to make the crossing because of the rough seas.Zanzibar’s transport minister told reporters that two Europeans were among the dead.The rescue operation had to be abandoned on Wednesday evening because of bad weather.The BBC’s Hassan Mhelela in Dar es Salaam says on Thursday morning there were many anxious relatives of missing MV Skagit passengers at the airport waiting to fly to Zanzibar.The route between Dar es Salaam and Zanzibar is a busy crossing, popular with both Tanzanians and foreign tourists. Last September, nearly 200 people died when an overcrowded boat with 800 people aboard sank off Zanzibar.