Cairo, Egypt ? Archeologists have unearthed 57 ancient Egyptian tombs, most of which hold an ornately painted wooden sarcophagus with a mummy inside, Egypt’s Supreme Council of Antiquities said Sunday.

The oldest tombs date back to around 2750 B.C. during the period of Egypt’s first and second dynasties, the council said in a statement. Twelve of the tombs belong the 18th dynasty, which ruled Egypt during the second millennium B.C.

The discovery throws new light on Egypt’s ancient religions, the council said.

Egypt’s archaeology chief, Zahi Hawass, said the mummies dating to the 18th dynasty are covered in linen decorated with religious texts from the Book of the Dead and scenes featuring ancient Egyptian deities.

Abdel Rahman El-Aydi, head of the archaeological mission that made the discovery, said some of the tombs are decorated with religious texts that ancient Egyptians believed would help the deceased to cross through the underworld.

El-Aydi said one of the oldest tombs is almost completely intact, with all of its funerary equipment and a wooden sarcophagus containing a mummy wrapped in linen.