Kampala - At least 20 people were killed when their boat capsized on Friday in Lake Victoria as it was carrying passengers to mainland Uganda for Christmas holidays, police said.The vessel was travelling from Bukasa island to the coastal town Entebbe when it flipped for reasons that are still unclear."About 20 confirmed dead, 10 have been rescued", area police commander Richard Musisi told AFP. "Of the 20 who died we have managed to retrieve four bodies from the lake.""We can't at the moment put a finger on what happened. Whether it was overload or the waves", he said adding none of the passengers were wearing life jackets.Bukasa's inhabitants are largely fishermen and farmers. It is a favourite for foreign tourists, though none were among the dead.Deadly accidents are common on Ugandan waters. In November about 10 people drowned when a boat capsized on Lake Albert in northeast Uganda.