MADRID -- Spanish authorities are seeking 90 million euros in damages from a Swedish mining company for a major toxic spill near the famed Donana National Park in 1998.

The civil trial that opened Tuesday is hearing the case against the Boliden company that ran the Los Frailes Aznalcollar mine where the walls of a wastewater reservoir burst, pouring an estimated 1.3 billion gallons of acidic liquid into the Guadiamar River in southern Seville province in what was one of Spain's worst environmental disasters.

Makeshift dikes kept the liquid and mud from flowing into the nearby Donana National Park, but a vast area near the mine was inundated with toxic sludge containing traces of zinc, iron and other heavy metals. Thousands of fish and birds were killed.

The southern regional government of Andalusia is taking the case against Boliden.

The trial will hear testimony from 12 witnesses and three experts and is expected to conclude July 13, court officials said.

A criminal trial was shelved in 2001 by a Seville court, which ruled that Boliden was not criminally responsible for the spill.

Boliden claims it had been authorized to increase the size of the reservoir at Aznalcollar before the walls broke, and that it later voluntarily cleaned up at a cost of some 80 million euros.

"At the time of the accident, Boliden took a very big responsibility and restored the area we were responsible for to levels better than before," Boliden press spokesman Klas Nilsson told The Associated Press on Tuesday.

"In addition, Donana remained completely unaffected by the accident, which was of course very important. The financial disagreement between Boliden and the region will now be tried, which we welcome, not least since the accident happened 25 years ago."

Donana, one of Europe's most prized reserves, covers 75,000 hectares along Spain's southwestern coast, providing shelter for millions of migratory birds and threatened species such as lynx and imperial eagles.

Environmentalists and politicians say the park is currently under serious threat from right-wing local lawmakers' plans to expand water rights for farmland around the wetlands amid Spain's prolonged drought.

The mine was closed in 2001 but a Mexican group has recently applied to reopen it.

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Jan M. Olsen in Copenhagen, Denmark, contributed to this report.