PARIS (AP) — France’s maritime minister has ordered an investigation into a possible violation of fishing practices after an environmental group released video and photos of a massive swarm of dead fish released by a huge trawler in the Atlantic Ocean off France.

The images by the group Sea Shepherd show a blanket of dead blue whiting fish floating on the surface of the Bay of Biscay, off the coast of southwest France. The group estimates it held some 100,000 dead fish.

Struck by the “shocking” images, French Maritime Minister Annick Girardin tweeted Friday that she ordered the National Center for Fishing Surveillance to investigate what happened.

The Pelagic Freezer-Trawler Association, which represents the trawler Margiris, which caught the fish, said in a statement that they were “involuntarily released into the sea" on Thursday because of a tear in the trawler's net.

“Such an accident is a rare occurrence, and in this case was caused by the unexpectedly large size of the fish caught," it said. It said the trawler has adapted its practices to deal with “the exceptional size of the fish currently in the area concerned.”

Sea Shepherd questioned whether it was an accident or an intentional dump of unwanted fish. The group is calling for more policing of the seas to protect sea life and oceans.