Law enforcement sources tell TMZ ... Bynes was intercepted by LAPD officers Saturday morning after a call came in for a woman who was in distress. That woman, as we've learned, is Bynes. We're told she was taken to a police station where a professional medical unit was standing by to check her out and determine if she needed further treatment.

As you can see, as part of this process ... Amanda was detained. Eyewitnesses tell us she was calm during the interaction with cops, and looked defeated as they dealt with her. We're told she was placed in the back of one of the 3 cruisers that arrived to her location.

It's unclear if Amanda was escorted out of her home, or if she was just found on the street here. We also don't know if she was ultimately taken to a hospital for a full-blown 5150 hold, or if she was released by LAPD. We're working on getting more info now.

This latest stumble follows a downward spiral the former Nick star has been on since being admitted into a mental hospital earlier this year -- this after she was found roaming the streets of DTLA completely naked, at which point she was placed on a psych hold.

Amanda has since been released from that mental health facility, but we've heard from people with direct knowledge that she hasn't been doing so great in the aftermath of that.

As we've reported ... AB has been living alone and doesn't have many people in her orbit. She tends to keep to herself, and we're told her attitude lately has been despondent. However, we do hear she's been good about taking her meds and seeing therapists.

Of course, her on-again-off-again fiance, Paul Michael, told us they split about a week before her breakdown in the spring ... and it doesn't appear they're back together at this point.

The larger backdrop to all of this is Amanda having been released from her multi-year conservatorship in 2022. Leading up to that, she appeared to be doing quite well for herself -- attending fashion school and seeming focused and relatively healthy amid a career change.