TELLING SIGN: Tibetan antelopes, which are known to be scared of noisy trains, appear to be oblivious to the speeding train. -- PHOTO: NEWS.XINHUANET.COM

One telling sign: Tibetan antelopes, which are known to be scared of noisy trains, moved in an orderly manner in the photo, oblivious to a train speeding past them.

The photo was taken by renowned Chinese photographer Liu Weiqiang and released by Xinhua in June 2006. It has since been published by more than 200 media agencies worldwide and won the bronze award in China Central Television's 2006 News Photo Of The Year.

The Chinese authorities have even used the photo to prove that the construction of the Qinghai-Tibet railway did not affect the ecological environment near the railway, according to Apple Daily.

The 1,142km railway is the world's highest, climbing 5,072m above sea level along the Tibetan plateau.

The forgery was first spotted by a netizen going by the name 'dajiala', who posted his discovery online. He said in his posting that there was an unnatural line near the bottom of the picture. He suggested that the photo was digitally altered and that the train and the antelopes were from two separate photos.

Chengdu Evening News contacted a veteran photographer who said it was impossible for a group of antelopes to move in such a straight line if the train was moving behind them, and went on to show a photo of antelopes scattering away when a train passed them.

Chengdu Evening News then contacted Mr Liu, who is currently the deputy head of the photo department with Daqing Evening News. He admitted merging two photos into one, but said that his photo was not meant to be released as a news picture, but as an 'art photo'.

However, he had claimed in an earlier interview that it took him eight days and eight nights before he snapped the photo.

State broadcaster CCTV has not reacted to the latest discovery.