Two pilot whales died and two were euthanized Monday in waters off of Florida's Lee County after wildlife officials monitored them all day, the National Oceanic and Atmospheric Administration said.
The whales were among about four dozen of the mammals seen swimming in shallow waters Sunday and Monday.
The whales were spread out, and there could be more stranded. Officials had closed off New Pass in order to help in the effort to save the whales.
About 12 to 20 whales from this pod were swimming freely in the area, said NOAA spokeswoman Kim Amendola.
Necropsies would be performed on the dead whales.
Additionally, there were 23 more whales swimming freely in Collier County on the north side of Marco Island. Wildlife officials were monitoring them.
On Sunday, these whales had been in shallow water near Gordon Pass but were able to swim to deeper Gulf waters.
Those whales appeared to be ill and emaciated and looked as if they had not eaten in a while. Experts weren't immediately able to determine the cause of their illness.
In early December, more than 50 pilot whales became stranded in Everglades National Park. Seven died and four were euthanized before the rest apparently swam back into deeper waters.
The pilot whale is a common species involved in mass strandings. Scientists say that if one pilot whale is sick, many other whales will get ill just because they are out of their normal environment.
Also, if the group somehow gets off course, it is difficult to recuperate and get back on course.