NANJING, April 6 -- Two Chinese men have been arrested for allegedly discharging hazardous acid waste into the Grand Canal, a World Heritage site, according to local procurators.

The suspects were accused of releasing the waste into the Suzhou section of the canal, the world's oldest and longest artificial waterway, since October, 2013, the procuratorate in Wuzhong District, Suzhou City, east China's Jiangsu Province, told Xinhua on Monday.

The two used waste acid to produce a water-purifying agent and then deliberately allowed the used material, stored in a leaky container, to enter the waterway which is only 10 meters from the container, according to the procuratorate.

Local environmental protection authorities ordered them to stop production of the agent in December, 2013. However, the suspects continued to collect waste acid from other factories, which paid them, 120 to 150 yuan (about 20 to 24 U.S. dollars) per ton, for disposal of the waste.

As of February, 2015, they obtained around 90,000 yuan from factories and simply let the waste leak into the canal.

Their trick was discovered by the local police last year after monitoring data showed abnormal fluctuation of water quality in the canal.

In June, 2014, UNESCO included the Grand Canal, with a history of more than 2,400 years, in the World Heritage list. The 1,011-km-long waterway, runs from Beijing to Hangzhou in China's eastern Zhejiang province, is the largest civil engineering project before the Industrial Revolution.