'Party Rock Anthem' Singer Lauren Bennett's Death Investigated as Suspected Suicide

Lauren Bennett most likely died by suicide, or at least that's how police are viewing her death ... TMZ has learned.

Multiple sources with direct knowledge tell TMZ ... authorities investigating the singer's May 29 death in the United Kingdom are treating the case as a suspected suicide.

As TMZ previously reported, the investigation remains ongoing and could take until October before it's formally concluded.

On Tuesday, Lauren's father, Richard Bennett, publicly criticized the medical care his daughter received in the months leading up to her death.

In a statement posted to social media Tuesday, Richard said Lauren experienced "a severe reaction to a prescribed medication" months before she died.

He wrote, "We have no suspicions regarding the circumstances of her death, only deep disappointment that, for five months, medical professionals and NHS services failed to treat her appropriately during her time of greatest need."

We broke the story ... a private memorial service was held in London about a week and a half ago, where Lauren's family and closest friends gathered to celebrate her life. Former bandmates from G.R.L. and Paradiso Girls were among those in attendance.

She was famously featured on LMFAO's "Party Rock Anthem" in 2011 -- one of the most popular songs of the year -- before joining G.R.L., which eventually disbanded in 2015 after dropping songs like "Vacation" and "Lighthouse."