The state has administered a second round of rodenticide bait drops to eradicate rats on Lehua Island.

A helicopter started the application at dawn Wednesday by spreading pellets containing diphacinone on the 284-acre island from a hanging bucket. The application was completed in about three hours, according to the Department of Land and Natural Resources.

The first of three rounds of rodenticide drops took place last week in an effort to a create a predator-free sanctuary for endangered and threatened birds. The final round is expected to take place in 10 days, weather permitting.

Some Kauai residents have raised concerns on whether the rodenticide poses a threat to marine life and the environment. The state said diphacinone, an anticoagulant, would have no significant impact.

Federal and state agricultural inspectors have been monitoring operations to ensure marine mammals and seabirds are not harmed.

Island Conservation, an organization involved in the project, is on-site, monitoring the area.

So far, the state reported 25 percent of about two dozen rats wearing radio tracking collars have died from the bait, as well as a “significant number” of rats without tracking devices, according to a news release.

The state indicated seabirds on Lehua Island are faring well. Prior to the first round of rodenticide baiting, the state said the field team discovered an average of one wedge-tailed shearwater chick carcass a day. Since the first bait application, there have been no reports of any predator-related deaths involving chicks.

Island Conservation plans to continue monitoring the site for a year to determine whether the rodenticide applications is effective in ridding the island of rats.

The organization has said 99.995 percent of the bait is composed of nontoxic, human food-grade material and the remaining fraction — five parts per million — is diphacinone.