CAIRO: At least nine people drowned when their boat sank on a family excursion on a lake just south of the Egyptian coastal city of Alexandria, the governor's office said on Tuesday.

Seven people survived the accident on Lake Mariout including five who required medical treatment, a statement said. A search was under way for an unspecified number of missing people.

The cause of the accident was unclear.

The boat sank after sunset on Monday, medical and security sources said.