Hundreds of police in Shanghai have been searching for a small cylinder containing a gamma-ray apparatus capable of transmitting fatal doses of radiation, Chinese state press reported on Tuesday.

The 10kg box containing the instrument used to perform industrial radiography on construction sites disappeared early on Saturday after a company driver parked a car carrying the cylinder outside his flat, the Shanghai Daily said.

When he returned, the canister clearly marked with a warning sign, was missing.

Press reports said a two-day search in the city's northern Jingshan district were yet to yield results. Police were not available for comment.

The company has offered a $1200 reward for information leading to the discovery of the hazardous material.

"As a professional, he should have never left such equipment out of his sight on the street, let alone leaving it unattended," the Shanghai Daily quoted Lu Shuyu, a radiation expert, as saying of the driver.