A United States federal jury in Washington DC has convicted New Zealand fishing company Sanford of dumping oil waste off American Samoa and falsifying records.
The jury also convicted one of the company's employees of falsifying records, the Associated Press reports.
The Auckland-based company faces fines of up to $US3 million ($NZ3.7m).
"We can't decide whether to appeal it or not until after the sentencing," says the company's managing director, Eric Barrett.
Prosecutors said Sanford's vessel San Nikunau dumped oil from its bilges without using pollution prevention equipment. They also said the company covered this up by falsely claiming such equipment had been used.
The case was brought by the US Attorney's Office for the District of Columbia and by the environmental crimes section of the Department of Justice.
The charges stem from an investigation by the US Coast Guard, which detained the vessel in American Samoa. Sanford had initially faced seven charges.
The San Nikunau is one of three large-scale freezer tuna purse seiners that Sanford operates in the Pacific. It targets skipjack tuna used for canning, which is typically unloaded and sold into one of the two canneries in Pago Pago.
NZN