Two of King's daughters claim that the blues legend died on May 14 as a result of being poisoned by his business manager, LaVerne Toney, and personal assistant, Myron Johnson.
"I believe my father was murdered," Karen Williams and Patty King each said in separate affidavits obtained by the AP.
Toney worked for King for 39 years and had been granted power-of-attorney over the musician's affairs. He is also the executor of King's estate, according to King's will. Johnson was at King's bedside when he died in hospice care earlier this month.
Patty King claims she saw Johnson administer drops of an unknown substance to her father's tongue in the days before his death.
Police in Las Vegas say King's death is under investigation and they are awaiting the results of an autopsy that was performed this weekend.