16 people were killed after a boat sank Wednesday night in a lake near the Albanian capital Tirana, police reported Thursday. Among the dead, there are the five-year old twins, whose birthday was being celebrated when the boat capsized and sank, according to the Associated Press.

The boat had a capacity of seven persons, but it was transporting 20 partygoers when it sank shortly after midnight in Lake Farka, about 10 km (6 miles) east of Tirana. The boat belonged to a restaurant located on the shores of Lake Farka, Tirana police spokeswoman Alma Katragjini informed.

The boat is believed to have capsized because it was overloaded. Only four people survived the accident. The rescuing authorities managed to recover the 16 bodies approximately three hours after the sinking: seven men, seven women and the 5-year-old twins, Katragjini said.

Fourteen of the victims were members of two families celebrating the birthday, while two of the bodies have not been identified immediately, but the authorities believe they were family friends.

Lake Farka is a popular location for Tirana residents. Most of the lakeside and seaside restaurants in Albania could be easily reached as they are connected to roads. The restaurant on Lake Farka was more remote, and it could be reached by a small boat. But such tragedies are not often seen in Albania.