HILO, Hawai'i — The U.S. Environmental Protection Agency is fining Kamehameha Schools $3,300 for using rodent poison improperly in an effort to control mongoose and rat populations in the Keauhou Ranch woodland area of the Big Island.

In addition to mongoose and rats, the poison set out by the school and the U.S. Department of Agriculture also killed a dozen or more feral pigs on the property in 2003, according to the EPA.

The EPA had issued an experimental use permit allowing a field test of an aerial drop of fish-flavored poison pellets, but school and agriculture officials also put the poison pellets in ground bait traps in violation of the permit, according to the EPA.

Kamehameha Schools yesterday acknowledged the bait killed "several pigs" after the pigs broke into the bait boxes. "We greatly regret the inadvertent deaths of the feral pigs," the school said in a statement.

The bait boxes were allowed, according to the school, but were supposed to be stocked with a block form of the same poison instead of the aerial pellets. School officials noted that they reported the incident to health, forestry and wildlife authorities immediately, and cooperated with the investigations into the deaths.

Air drops of poison pellets are used successfully in New Zealand and on the Channel Islands off the California coast, but are not widely used in Hawai'i.

The experiment in Keauhou was "of great interest to bird and forest conservation groups and other Hawai'i landowners, including the state and federal governments, as a potentially effective, efficient method of controlling feral rat populations in highly sensitive areas," according to Kamehameha Schools.

Rats and other rodents have taken a heavy toll on Hawai'i's native birds, and slow the natural recovery of native forest and grass species because they forage on seeds and young sprouts of native plants.