XI'AN, May 21 -- Police have defused three 1930s Japanese bombs found in a construction site in northwest China's Shaanxi Province on Wednesday afternoon.

The three rusty aerial bombs were discovered by workers renovating a public garage in the city of Baoji. Two were found by chance, when an excavator dug them up from buried positions, while police officers called to the scene later found another one, said local authorities on Thursday.

Police cautioned the construction workers of the possibility of them finding more live bombs in the area.

According to Tian Hucheng, director of the air defense office of Baoji, the bombs bore the Japanese characters for the year1939.

Academics generally agree that all-out war between China and the invading Japanese started in 1937, with the conflict lasting eight years.

"Due to its geographical importance, Baoji was a major target for Japanese bombs," Tian said.

Between April 1938 and April 1944, a total of 334 Japanese airplanes dropped 1,372 bombs on Baoji, killing 578 and injuring502, according to the air defense office.