By Ho Binh Minh
HANOI (Reuters) - Vietnam has told owners of a Taiwanese-built steel plant to dig up a controversial waste pipe, even after it found no evidence tying its discharge to mass fish deaths that have triggered health fears and public anger.
Huge numbers of dead fish have appeared at farms and on beaches in central Vietnam since April 6, impacting 200 km (124 miles) of coastline, with no known cause of what the government is calling one of its worst ever environmental disasters.
Environment Minister Tran Hong Ha declared illegal the waste pipe operated by Hung Nghiep Formosa Ha Tinh, a unit of Formosa Plastics, after officials examined water samples around the site.
"We propose to have measures in place to monitor this system after it is elevated, for easy access and surveillance," Ha told Formosa officials and reporters on Thursday.
Ha's comments suggest the government retains doubts despite tests that show Formosa, a major investor leading the $10.6 billion steel project, was not behind the pollution.
Public outrage was also evident on social media, the only real channel through which Vietnamese get to vent in a country tightly controlled by the Communist Party.
In a statement on Friday Ha admitted the government lacked experience in dealing with disasters and had been slow to act. He called it a "very huge and serious environment disaster".
The government has banned sale and distribution of non-living aquatic products in four affected provinces.
Its probe said toxic discharge caused by humans or "red tide", when algae blooming at an abnormal rate produce toxins, may have killed the fish.
Facebook, which is used by some 30 million Vietnamese, is seeing an outpouring of anger directed at Formosa and criticism of the government's sluggish response.
Many used the hashtag #toichonca, which means: "I choose fish".
The hashtag emerged after a Taiwanese official at Formosa Ha Tinh said Vietnam had to choose between "catching fish and shrimp and building a modern steel industry". He later apologized.
In a government letter issued on Friday, Prime Minister Nguyen Xuan Phuc said authorities had yet to find the cause, and acknowledged public concerns.
Vietnam's seafood exports, which totaled $6.6 billion last year, will not be hurt, the industry's body said. Top buyers are the United States, Europe and Japan.
A petition on the White House website is urging President Barack Obama to raise the issue with Vietnam's leaders when he visits next month.
(Additional reporting by My Pham; Editing by Martin Petty and Simon Cameron-Moore)