Archaeologists said Tuesday they have unearthed 22 graves in northern Peru containing a trove of pre-Inca artifacts, including the first "tumi" ceremonial knives ever discovered by archaeologists rather than looted by thieves.

The find, which prominent archaeologist Walter Alva called "overwhelmingly important," means that scientists can study the tumi — Peru's national symbol — in its original setting to learn about the context in which it was used.

"This discovery comes as an important contribution to know the burial rites of the elite of this culture," said Alva, who was not involved in the dig.