Three girls kayaking on the Hanalei River on Tuesday reported they saw what looked like a 2 1/2-foot-long gray snake.

They said the creature appeared to drop from the branch of a java plum tree and land in the water, said Ed Pickop, a plant quarantine inspector for the state Department of Agriculture.

Agriculture officials and a staffer of the Kaua'i Invasive Species Committee interviewed the girls — a 16-year-old and two 8-year-olds — and did a search of the area Tuesday. They were back in the river yesterday, continuing to look for evidence of the snake, or whatever it might have been.

Pickop said the investigators found no sign of a snake during their preliminary search.

Kaua'i Invasive Species Committee coordinator Keren Gundersen said the description of the snake was not sufficiently clear to identify its species.

"In my opinion, it was unlikely it was a brown tree snake, because this was seen during the day," while brown tree snakes — which have caused severe harm to native wildlife in Guam — are nocturnal, she said.

Pickop said there has been at least one other report of a snake seen in or around the Hanalei River.

"We're taking this very seriously," he said.

Snakes are not native to Hawai'i.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.