By Mai Nguyen
HANOI (Reuters) - Vietnam said on Thursday a $10.6 billion steel plant run by a unit of Taiwan's Formosa Plastics caused an until-now mysterious environmental crisis by releasing toxic wastewater into the sea.
Formosa Ha Tinh Steel, which operates a new plant set to become the biggest of its kind in Southeast Asia, on Tuesday admitted responsibility for a disaster that caused massive fish deaths in coastal provinces in April, said Mai Tien Dung, head of the government office.
The spill sparked public outrage across Vietnam and three successive weekends of protests, with demonstrators venting their fury at both Formosa and the government, accusing them of a cover-up.
Formosa had apologized and would provide $500 million in compensation for those affected, Dung said.
"Violations in the construction and testing operations of the plant are the causes for serious environment pollution killing a massive amount of fish," Dung told a packed news conference.
"Formosa has admitted responsibility for the fish deaths in four central provinces and committed to publicly apologize for causing severe environmental incidents."
The plant is one of the single biggest investments by a foreign firm in Vietnam.
Media reports in April said chemicals from a drainage pipe killed the fish, but a preliminary investigation by Formosa and separately by the government said there were no direct links between the steel plant and the fish deaths.
The initial government probe concluded the cause was either toxic discharge caused by humans or "red tide", when algae blooming at an abnormal rate produce toxins.
The incident created a crisis for a new government led by Prime Minister Nguyen Xuan Phuc, which took office within days of when dead fish started washing up on beaches on April 6, impacting 200 km (124 miles) of coastline.
The first protests in several cities were initially tolerated by the authorities, but later rallies were broken up by police, who were accused by rights groups of using heavy-handed measures to stifle free speech.
Protests also took place in the days ahead of a landmark visit by U.S. President Barack Obama. A petition posted on the White House website demanding a transparent probe received 140,000 signatures.
Vietnam said the rallies were orchestrated by "reactionary forces" bent on trying to bring down the government.
In a video clip played at Thursday's news conference, Tran Nguyen Thanh, the chairman of Formosa Ha Tinh Steel, expressed regret over the incident.
"We deeply hope the Vietnam people can forgive us," he said.
(Reporting by Mai Nguyen; Writing by Martin Petty; Editing by Nick Macfie)