In an Instagram message Thursday, Brit says she realizes she scared people with her video post showing her dancing with knives. Some of her supporters were so spooked they called the cops, who arrived on Brit's doorstep for a welfare check.

But, Brit insists the knives are "fake" as she has said before -- and now she claims her team rented them from "Hand Prop shop" in Los Angeles. (She might have meant "The Hand Prop Room.")

Driving the point home, Brit writes, "These are not real knives. No one needs to worry or call the police."

She went on, "I’m trying to imitate one of my favorite performers Shakira … a performance I was inspired by !!!"

Brit ended with ... "Cheers to us bad girls who aren’t afraid to push boundaries and take risks."

All the drama began Monday when Brit posted the IG clip of herself pirouetting with very real-looking knives in each hand. Brit wrote in the caption, "I started playing in the kitchen with knives today." Later on, she added the knives were fake Halloween props.

One of the reasons people were skeptical of her story ... you hear the clanging sound of knives when they touch.

Not long thereafter, Britney posted another video with a bandage around one of her arms and a cut on her leg. She didn't say how it happened, but lots of people were alarmed.

Not everyone believed Brit, and several people called the Ventura County Sheriff's Department out of concern. TMZ broke the story Thursday ... deputies responded to Brit's home for a welfare check ... but Brit's security said she was fine and that was that.