Vietnam is investigating a massive fish kill at aquatic farms and in waters off the country's central provinces that state media reports have tied to alleged toxic discharges coming from a steel complex built by Taiwan's Formosa Plastics.
The Taiwan's company local unit Hung Nghiep Formosa Ha Tinh Steel Corp, however, said in a statement this week via its parent company that there is no evidence that wastewater from its steel plant was responsible for the fish deaths.
Fish raised in farms near Vung Ang port in Ha Tinh province, about 400 km (250 miles) south of Hanoi, began dying on April 6, with more dead fish subsequently washing up on nearby beaches, the Vietnamese government said in a report.
The fish deaths in Ha Tinh and now other provinces have raised concerns about food security and domestic seafood markets could threaten Vietnam's $7 billion in annual seafood exports.
"I've been doing this job for 19 years but I've never seen such a phenomenon," clam farmer Nguyen Xuan Phuong in Ha Tinh province told state-run Vietnam Television (VTV) on Tuesday.
Fish and shellfish deaths have now also been reported in the provinces of Quang Binh, Quang Tri and Thua Thien-Hue along a stretch of some 200 km (124 miles) on Vietnam's central coast.
Several media reports have said a drainage pipe operated by Formosa's Vietnam unit in Ha Tinh province is behind the water pollution that has killed the fish.
Tests of seawater taken from Thua Thien-Hue province showed higher-than-normal contents of ammonium - a nitrogen compound - and chromium, deputy head Nguyen Huu Quyet of the provincial environment department said on Wednesday in a VTV broadcast.
Formosa Ha Tinh is building a $10.6 billion steel complex in the Vung Ang economic zone, and the first phase of the steel plant began operating in December 2015.
Controversy over the plant and the fish kill was exacerbated when Chu Xuan Pham, a Hanoi-based representative of Formosa's local unit, said in comments reported on Monday that Vietnam has to choose between "catching fish and shrimp and building a modern steel industry."
Chu apologized for his comments at a news conference on Tuesday in Ha Tinh province, and Formosa Ha Tinh said in the statement via its parent: "We are deeply shocked and sorry. We cannot understand why so many fish have died."
Vietnamese newspapers reported on Wednesday that Chu has since been fired, although this could not be confirmed with the company and Chu could not be reached for comment.
The wastewater discharged by Formosa Ha Tinh has undergone proper treatment and meets with Vietnam's standards, the local company's director of environmental hygiene and safety, Khau Nhan Kiet, said at Tuesday's news conference.
Vietnam's Prime Minister Nguyen Xuan Phuc, who took office early this month, has ordered a thorough inspection of the fish deaths, the government said on Tuesday without naming any suspects. The findings are expected out later this week.
Taiwan ranks Vietnam's fourth-biggest foreign investor after South Korea, Japan and Singapore.