Meghan Markle's Estranged Dad Thomas Arrested in Florida for Possession of Child Porn

Meghan Markle's estranged father, Thomas Markle Sr., has been arrested in Florida for possession of child sexual abuse material ... following weeks of disturbing allegations ... TMZ has confirmed.

FBI agents arrested the 82-year-old Friday at his senior living facility in Lakeland.

Federal prosecutors say Thomas is charged with possession of child pornography after agents raided storage units he was renting in California, and found explicit photos of Thomas with prepubescent girls.

Thomas was already under investigation in the Philippines after authorities uncovered thousands of alleged child sexual abuse images linked to his former home.

Philippine Interior Secretary Jonvic Remulla revealed Thursday that investigators recovered roughly 7,500 photos and a video depicting alleged sexual abuse of boys and girls of Asian, Latin American and European descent ... some as young as 10 or 11.

Remulla described the material as "deplorable" ... though authorities have not determined who owned the devices containing the images.

Thomas previously denied the allegations, calling them "sick lies."

The investigation began after Thomas' son, Thomas Markle Jr., claimed he discovered hundreds, if not thousands, of disturbing images among his father's belongings at his former home in Cebu.

In another twist ... Thomas Jr. has since been named a person of interest in the Philippine investigation, though authorities stressed he is not currently considered a suspect.

Meghan previously said she was "deeply distressed" by the allegations against her father ... claiming she'd received troubling information about him years earlier and kept him away from her children to protect them.