COLLIER COUNTY, Fla. -

The Florida Fish & Wildlife says 25 pilot whales were found dead Thursday south of Marco Island in the Ten Thousand Islands.

These are the same whales that were in Gordon Pass in Naples on Sunday and in Marco Pass on Monday, according to the National Oceanic and Atmospheric Administration.

However, officials said the pilot whales are not the whales involved in the stranding at New Pass on Lovers Key, in Lee County.

Dead pilot whales off Fla coast

Courtesy: Naples Daily News & Amelia Tripp

Officials said the whales were spotted by a boater Thursday afternoon. There are 16 females and nine males, according to NOAA.

A cause of death was not provided, but biologists are investigating sonar as a possible cause, as they do whenever there is a mass-stranding.

The whales were described by officials as underweight and looking very thin.