National wildlife officials say 11 whales believed to be part of a pod that was stranded in the Everglades are dead.
National Oceanic and Atmospheric Administration official Blair Mase says wildlife workers spotted the dead whales Sunday afternoon on Snipe Point, about six miles north of Sugarloaf Key.
That brings the overall death toll to 22.
The pod of 51 short-finned pilot whales was first spotted by a fishing guide Tuesday in the shallow waters off a remote section of the Everglades. The species is one of the most commonly involved in mass strandings.
Mase says that veterinary teams will try to determine whether any disease was a factor in the deaths.
Officials do not know the status of the remaining whales. The marine mammals were last seen alive Friday.
"Given our knowledge of past mass pilot whales strandings, the outlook for finding the remaining whales alive is bleak," the Coast Guard said in a statement. It's possible, they note, that the 29 other whales may have already died and sunk to the ocean floor.
Experts are still trying to determine what killed the whales. Necropsies performed on the first 11 dead whales were looking for possible diseases, biotoxins, red tide or even human-related causes. The Coast Guard also said they saw no evidence of sonar trauma but would make further inquiries with the U.S. Navy.
Some material from Reuters was also used in this story.