Three chemical factories found illegally dumping wastewater into city sewage systems and the sea have had their cases turned over to police.

After being investigated and fined by the local environment authorities,the three factories in Lianyungang city in East China's Jiangsu Province will now be probed for possible criminal charges.

In one case, a company built its own pipelines to dump toxic wastewater into the sea.

The three cases are very serious and have left a large environmental impact, said a statement by the Ministry of Environmental Protection released in Beijing on Monday.

In April, the China Youth Daily carried a report that locals at Guanyun county of Lianyungang discovered underground pipelines that discharged "scarlet water" into the nearby bay and seriously polluted the sea water.

Environment departments across the country have stepped up their efforts against polluters. In August, they closed investigation into 45 serious pollution cases, according to the ministry.