9:02 AM PT -- Law enforcement sources tell TMZ ... Bark n' Bitches is under investigation. We're told the City of L.A. Department of Animal Services is conducting the investigation. What's more ... sources say the LAPD's Animal Cruelty Taskforce is aware of the incident.
And, get this ... a separate complaint prior to the horrific dog-throwing incident triggered the Department's probe. It's unclear what sparked the initial investigation, but we're told the Animal Cruelty Taskforce fielded the complaint.
We've reached out to the Dept. of Animal Services ... so far, no word back.
A poor pup was violently launched across a room by her neck by an irate employee and landed on her head on a concrete floor ... and the disgusting incident was caught on video.
The vid shows several dogs running around and barking in the Bark n' Bitches Dog Boutique in L.A. when it appears one dog begins to play a little too aggressively with a smaller dog.
That's when the worker steps in and viciously grabs the larger dog by the neck, picks her up high and tosses her several feet ... to the shock and horror of others in the store.
After the throw, a sickening thud is heard as the dog hits the ground. The sound is the dog's head hitting the floor ... according to the person who first posted the video on Twitch.
Some of the people in the store go to check on the poor pooch afterward, as it hid under a nearby table.
Bark n' Bitches has responded to the horrific incident, saying ... "We will not tolerate this or any actions that put our rescues in harm's way. The appropriate actions are being taken. This is NOT what we stand for."
It added ... "The dog was playing and acting normal after this incident. She was taken to the vet and was cleared 100 percent."
The owner of the shop followed up by confirming the employee in the video has been fired and the dog is doing fine. The owner added the boutique has been in business for 14 years and "this is a first."