The prosecutor's office in the southern town of Ales said it had launched a preliminary probe into the local slaughterhouse for "acts of cruelty" and "mistreatment of animals".
The inquiry was triggered by a complaint filed by the L214 animal rights group, which published a video this week showing the treatment of cattle, horses, pigs and sheep at Ales abattoir.
Filmed between April and May, the video shows sheep and cattle having their throats slit and being left to bleed to death while conscious, after rousing from the torpor caused by a stun gun.
It also shows pigs crammed into a cage being lowered, writhing and squealing, into a pit to be gassed with carbon dioxide and a terrified horse who shies away from a stall being beaten with an electric prod.
On Wednesday, the mayor of Ales ordered the abattoir's provisional closure.
Brigitte Gothière, co-founder of L214 told The Local on Thursday that her group welcomed the closure.
Actress and animal rights campaigner Brigitte Bardot said the methods used to slaughter animals "recall the methods used in Nazi (extermination) camps).
Luc Hincelin, the official who oversees livestock rearing in the Gard department, where Ales is situated, agreed the images were "shocking".
"There are certain acts that are unacceptable which we cannot tolerate," he told AFP.
A veterinary expert who viewed the images for L214 said some of the procedures violated rules on the slaughter of animals and risked causing the carcasses to be contaminated with faecal matter.
The abattoir owner has filed a criminal complaint for "violation of privacy" over the appearance in the video of some staff members. The workers' faces were blurred in the footage.