A boat carrying 20 people celebrating the birthday of 5-year-old twins sank overnight in a lake near the capital, killing 16 people, including the two children, police said Thursday. The boat belonged to a restaurant on the shores of Lake Farka, about five kilometers (three miles) east of the capital, Tirana. It had a capacity of seven, but was transporting 20 partygoers from the restaurant when it sank shortly after midnight, Tirana police spokeswoman Alma Katragjini said. Authorities believe the boat capsized because it was overloaded. Four people survived, Katragjini said. By 3am , authorities had collected 16 bodies from the lake: seven men, seven women and the 5-year-old twin boys, she said.