Wondering what the #FreeBritney movement is after seeing the hashtag plastered all over social media? The fan campaign to "free" the pop star after being allegedly held in a mental health treatment facility against her will has a complicated history.

In March, Britney Spears checked herself into a 30-day program reportedly to deal with the stress she was experiencing from her father Jamie Spears' health problems. However, there are fans who believed the "Baby One More Time" singer is undergoing treatment against her will. This led to the creation of the now-viral hashtag #FreeBritney.

Fans became even more convinced of their theory after a recent episode of Britney’s Gram podcast featured "an anonymous tip from a credible source.”

The source, "a paralegal who used to work for an attorney that was involved in Britney’s conservatorship," claimed the 37-year-old has been kept in a mental health facility since January... not March. Spears' dad has been her conservator since 2008, which means he has the power to make decisions regarding her finances and personal life.

The unidentified man left the podcast's hosts a disturbing voicemail detailing allegations surrounding Spears' treatment:

“It came to Jamie’s attention that Britney was not taking her medication as prescribed. She was missing a lot of doses and just full-on not taking them. So they got her to the doctor and the doctor said, ‘OK, if you don’t want these medications, let’s get you on a new one.’ She refused to take the new one. Jamie said, ‘Either you take this medication or the show’s off, and I’m pulling my support and you can’t do it.’ Britney did not follow Jamie’s instructions, so he was true to his word—he pulled the show, he verbatim said, ‘Blame it on my illness.’ […] Britney has been in the mental facility since mid-January.”

You can listen to the voicemail at the around the 8-minute mark:

In January, the performer opened up about her dad's health struggles and announced she was taking an indefinite hiatus ahead of her scheduled Domination residency in Las Vegas. Then, Spears — who's known for being a frequent poster on Instagram — stopped sharing content, which fans used as more reason to believe the rumors were true.

But following the podcast, the pop star's mom, Lynne Spears, added fuel to the speculation when she started liking Instagram comments from fans who believed she was being held against her will. Lynne also liked another post urging people to listen to the podcast.

As a result, some fans became so convinced Spears has been held against her will that they held a protest on Monday (April 22) in Los Angeles demanding she be released.

Spears herself has yet to comment on the rumors, but her sister Jamie Lynn Spears recently fired back at the #FreeBritney trolls by posting a throwback video that sees her defending Britney against a swarm of paparazzi back in 2007.

"10 years ago, who was there?? I have been here long before anyone else and I’ll be here long after," she wrote alongside the clip. "I love my sister with everything I have, she wrote alongside the So anyone or anything that speaks to the contrary can GTFOH with all the comments about what you don’t understand."

Spears has been spotted in public two times since entering treatment. First, she was seen getting her hair done at a salon a few weeks ago. She was then photographed spending Easter with her boyfriend Sam Asghari at the Montage Beverly Hills Hotel.

According to reports, she looked "happy and relaxed."