Two more local environmental officials have been detained for their inadequate supervision in the recent toxic wastewater leakage at a copper mine in Shanghang county of East China's Fujian province, local prosecutors said on Tuesday.

Bao Weidong and Wu Shenglong, director and deputy director of the Zijinshan environmental supervision station, have been held in criminal custody for dereliction of duty since the weekend, said procuratorate officials of Longyan city, which administrates Shanghang county.

The station is responsible for checking the validity of the Zijinshan Copper Mine's wastewater treatment system.

The mine had a wastewater leakage on July 3, resulting in 9,100 cubic meters of toxic wastewater spewing into the Tingjiang River. The mine sprang another leak in its lash-up wastewater tank last Friday.

Worn equipment contributed to a split in the tank, and the wastewater allegedly passed through an "illegally built passage," officials with the Shanghang environmental protection bureau said.

Bao and Wu are blamed for failing to monitor the wastewater systems at the copper mine.

Meanwhile, the toxic water from Friday's leakage had sailed downward and reached Guangdong province. The copper content in Meizhou doubled last Friday, and continued to rise over the weekend.

Besides copper, Guangdong also found the water contained a cancer-causing substance named sexavalent chrome, China Business News reported on Sunday.

However, officials at the Guangdong environmental protection department said they did not find the substance in the water test. And the Fujian authority said the sexavalent chrome in its water could "meet the third-class of water quality", which means the water is safe for drinking after processing.

But local residents said they dared not drink the water.

"I buy bottled water to cook dishes because most people think they would get cancer if they drink the water here," said a restaurant owner surnamed Chen.

A water peddler in Shanghang told China Daily that he could sell out almost 100 bottles of water, each weighing 25 kg, since the pollution was exposed. He also said at least 5,000 bottles could be sold every day in the county.

Earlier last week, three staffers with the copper mine were detained. Local media reported that a total of 38 officials in Fujian would face administrative punishment.

In the wake of the incident, China Security Regulatory Commission (CSRC) also stepped in to investigate Zijin Mining, a listed company and owner of Zijinshan Copper Mine, for violating information disclosure rules, the company said on its website late Monday.

The leakage happened on June 3, but Zijin Mining did not announce the incident to stock buyers until June 12 when the pollution leak was reported by media.

Between June 3 and June 12 its share price rose 6.2 percent from 5.64 yuan ($0.83) to 5.99 yuan, and dropped 13 percent in the four days that followed.

Zijin Mining expressed "deep regret regarding the incident and the improper handling of information disclosure" in another statement on its website.

The company also revealed that it had been under investigation of the CSRC for similar reasons on March 30.