Eleven pilot whales were found dead and stranded in the Florida keys on Sunday, Dec. 8. Wildlife officials are investigating the possible causes, and so far only tragic details have been emerged.

The first important notes officials have found were that all the whales were female or young calves, and they all came on shore within feet of one another on a small beach. Two of the females were also pregnant. The National Oceanic and Atmospheric Administration’s Fisheries Service released these details on Monday.

This is not the first account of the pilot whales breaching themselves. A group of 51 whales that had gotten stranded in the Florida Everglades last week, which is about 70 miles from the island. Of those 51, 11 of the whales—three males and eight females—died. The pilots found dead last Sunday had similar markings to the ones found in the Everglade, leading officials to believe they were part of the same pod.

Researchers have been trying to determine whether disease or something else was the cause for the whales to swim to shallow waters and breach themselves. What the researchers do know is that pilot whales are extremely social and tight within a pod, so much so that they may refuse to leave sick members and breach themselves as a whole group.

Scientists were performing necropsies on Monday to look for clues that lead to the whales’ deaths. The 11 whales were malnourished, but officials have yet to confirm whether that was from disease or prolong time spent outside their natural habitat in the deep waters. According to the fisheries service, pilot whales normally eat squid at 1,000 feet below the surface or deeper.

However, it’s not uncommon for pilot whales to swim along the Florida coast and end up breaching themselves on the Keys, said one official.

“It’s basically history repeating itself,” Blair Mase, NOAA’s southeast region marine mammal stranding coordinator, said to reporters Monday. “When they do strand in that southwest Florida coast, we have seen them also come down to the Keys as well…. If they all don’t strand at the same time, they would end up in this general location.”

Officials said that another group of pilot whales had breached themselves near Fort Pierce, Fla., last year, which resulted in at least 17 of the 22 whales in the pod perishing. Another stranded group was reported in 2011 at Florida’s Cudjoe Keys. These mass breachings have been documented for decades, and research has a long way to go to determine their cause.