The vessels capsized after hitting a steel pole supporting a pontoon near the fertilizer factory of PT Pusri in Palembang.
Palembang police spokesman Adj. Comr Benni Wijaya said apparently the vessel pilot did not see the steel pole as it was hidden below the water surface as it was in high tide.
The vessel was on its way from the Ampera port of Palembang to Banyuasin.
The pilot Eka is still detained by police for questioning.
One of the dead victims, a man, is not yet identified. The other five were Dian Lestari (29), Fahri (7), Mahdalena (48), Sri Kadar Wati (40). (*)