9:38 AM PT -- Law enforcement sources tell us the initial call for the welfare check was made by a member of the LAPD Smart Team (a group that handles mental evaluations). Cops made the decision to go to Britney Spears' house because the person actually had some knowledge of Britney and her situation and wasn't just a fan.

Once officers arrived, they spoke with Britney's security who assured them she was OK, but didn't want to speak ... so the deputies left.

Britney's attorney called the cops later that day, asking about the visit, and deputies assured him they only made the visit because the call was made by someone who knew Britney ... they don't make the welfare checks for fan calls.

Britney Spears' latest Instagram stunt was enough to get the attention of police ... who visited the singer's home to make sure she was safe.

Law enforcement sources tell us they received a call Wednesday expressing concern for Britney based on her recent conduct on social media. We're told deputies were also familiar with the knife video, and out of an abundance of caution, deputies from the Ventura County Sheriff's Department went out to Britney's house.

We're told Britney was home, and deputies were able to speak with her and determine she was OK ... so they left.

Sources with direct knowledge tell TMZ ... several people called the cops after Britney posted the knife video, and one of them is a person who actually did a welfare check on her in the past and was alarmed.

The situation isn't all that surprising given the amount of concern expressed for Britney's safety this week after she posted a video of herself dancing with two knives. Spears claimed the knives were fake, but they certainly sounded real when she banged them together.

In another video, posted about an hour after Britney showed off her knife skills, she appeared to have a gash on her leg and had a bandage wrapped around her arm.

While she didn't specifically say how she sustained the new injuries, many believe they were caused by the knives ... which may have led to the welfare check calls.

It was earlier this year when cops performed a welfare check at Britney's home after fans became concerned for her safety when her Instagram account disappeared. Britney was fine, later reactivating her account and telling fans she appreciated their concern but was still annoyed to have the cops show up at her house.

As we first told you, Britney's fans have grown concerned for her small dogs as well. The pets looked scared in the background of her knife video, but authorities haven't taken action.

We covered it all on the latest episode of The TMZ Podcast, available on all podcast platforms.

Do you think Britney Spears' situation has reached the point of needing police to step in? Vote below.