A massive refinery fire in Nicaragua caused an oil spill that has contaminated sensitive nearby coastal habitat, a nonprofit group here said.

In the aftermath of the refinery fire at the Puma Energy facility on Nicaragua's Pacific coast, oil has slickened nearly one-half of a square mile of the nearby water and soil, said Victor Campos, director of the Humboldt Center, an environmental group.

Meanwhile, authorities said Saturday they hope to soon have the fire contained at the facility, this Central American nation's sole oil refinery.

The fire, which has been burning since Wednesday, began when one of four huge fuel tanks exploded at the site in the port of Puerto Sandino, some 70 kilometers (40 miles) northwest of the capital Managua. A second tank ignited on Thursday.

Oil from the spill could be seen on the coast and in surrounding vegetation in photos provided by Campos, who said that the damage done to the area would take years to reverse.

Environmentalists said the affected area includes ecologically sensitive habitat.

Surrounding beaches are home to important nesting grounds for several turtle species, while the Puerto Sandino coast and nearby Miramar beach produce 12 percent of Nicaragua's salt.

The area has "a number of natural resources as well as people, agriculture, livestock, local fauna, coastal marine life and birds," said resource specialist Ruth Herrera.

She added that environmentalists also expect that some wells in the area will also be contaminated.

Each of the damaged fuel tanks is capable of holding some 144,000 barrels, although the company ruled out a fuel shortage following the fire.

The Nicaragua and Puma energy said Saturday that they hope to extinguish the fire within hours, and said that the company would be strengthening its water contamination monitoring and surveying the environmental impact.

A huge plume of acrid smoke at one point billowed up to 3,000 meters (9,800 feet) at the disaster scene, but has largely dissipated, local media said.

Puma Energy, a majority Dutch- and Angolan-owned company with headquarters in Switzerland, bought the refinery in 2011. It had previously been run by the US group Exxon.