FILE PHOTO: Workers of Eviro-Tec and Nalco leave the alumina refinery Alunorte, owned by Norwegian company Norsk Hydro ASA, after an inspection operation with Brazilian environmental agency Ibama and Evandro Chagas Institute to verify a report of irregularities on bauxite residue deposits at Alunorte, in Barcarena, Para state, Brazil March 8, 2018.. REUTERS/Ricardo Moraes

OSLO (Reuters) - Norwegian aluminum maker Norsk Hydro’s Alunorte alumina refinery in Brazil made unauthorized spills of waste water last month, the company said on Sunday, more than two weeks after local authorities first began to raise questions.

Heavy rain and flooding at the plant in mid-February sparked fears of a leak of toxic bauxite waste around the facility and government warnings of contamination, but Hydro has so far maintained it had found no evidence of emissions.

Authorities in late February ordered the plant, the world’s largest alumina refinery, to cut output in half until it addressed concerns, leading Hydro to declare force majeure with no time set to restart production.

A Brazilian government-backed research institute on Friday told Reuters it will soon publish evidence of a waste leak from Alunorte, located in the northern state of Para.

Hydro spokesman Halvor Molland said on Sunday the company on two occasions decided to emit water after heavy rain had put pressure on the plant’s treatment facility.

“The canal we used for these emissions is not covered by our permit,” Molland said, while adding the company had later notified regulators.

“We have no indications that this controlled emission had a negative impact on the environment,” he added.

Hydro’s admission that spills had taken place was first reported by Norwegian business daily Dagens Naeringsliv.