One ton of ancient coins dating back about 900 years were unearthed Sunday at a construction site in northwest China's Shaanxi Province.

The coins were found in a brick cellar about 6-7 meters underground when an excavator was working on the site in Pucheng County. The owner of the coins remained a mystery.

A witness said the cellar was full of scattered coins and others bunched with rotten leather strips. Many coins are rusty.

Some coins have been confirmed to belong to Northern Song Dynasty (960-1127) while others unidentified because of erosion.

Local authorities on cultural relics have put the coins into protection.

In January, archaeologists in the history-laden Shaanxi discovered an ancient tomb in the suburb of the provincial capital Xi'an, possibly of a coin collector dating back more than 600 years.

Archaeologists found over 150 coins of different dynasties, which might have been collected by the owner of the tomb who was interested in ancient coins.