State and federal officials say a poison used to eradicate rats from Mokapu Island hasn't been detected in the marine environment.

Samples of seawater, opihi and fish were collected around the island north of Molokai after pellets containing the poison diphacinone were dropped from the air in February.

Officials say mainland tests conducted by the U.S. Department of Agriculture failed to find the rodenticide in any of the samples.

The eradication effort will be declared a success if no rats are found on Mokapu in two years. The project is the first step in the restoration of the native ecosystem on the island.