Police probing the little girl's death have confirmed that a pillow, blanket and baby wipes were discovered in the family home on January 17 -- three days after she had been brought to hospital.
The investigation team returned to the second floor apartment in Boston accompanied with crime laboratory specialist and found the items.
According to new court records, the baby wipes were "discarded" in a bin beside a changing table.
The blanket and pillow, which were discovered in the baby's cot, all had "red brown" blood stains.
"Observed during that search were baby wipes, found discarded in the Diaper Genie next to the changing table, with red-brown stains that tested positive in the screening test for blood as well as a blanket and pillow in the crib in the same room, with red-brown stains that tested positive in screening tests for blood," police reports have stated.
The wall next to the child's changing table also had "a piece of drywall/plaster missing" with "remnants" scattered on the floor that was "consistent with it being damaged by forceful contact with the corner of the changing table," police said.
A police report released last night concludes with a statement from an investigating officer during which he says he has "probable cause" to believe that Ms McCarthy Brady assaulted the baby.
"Based on my training and experience and conversations with the medical team treating and consulting on Rehma's case, I believe I have probable cause to believe that Aisling McCarthy Brady committed the crime of assault and battery on a child causing substantial bodily injury," he said.
The shocking new details relating to the US assault case comes as doctors prepare to release their medical report into the one-year-old's death.
Her parents, Sameer Sabir (34) and Nada Siddiqui (29), have told police that they do not know why there was blood in their baby's cot and bedroom.
Preliminary postmortem examination results conducted on January 19 show that there were "bruises to the top of and behind [the child's] right ear and her buttocks."
The analysis also revealed "multiple" bruising under Rehma's scalp as well as injuries to her spinal chord.
The police report revealed that the nanny "had sole custody of and contact with Rehma Sabir after 9.30am until Rehma was found seizing in her crib at 4.30pm.
The document added: "Rehma Sabir was sitting on her own, feeding and playing at the time (the mother) left the home that morning."
The documents state that Ms McCarthy told officers she became "a little concerned" at 4.15pm on January 14 when Rehma was still napping.
She said that she noticed the child was clenching her fists and her arms, adding that her legs were stiff.
She claims that when she picked up the toddler, she appeared limp.
The nanny stated that she told a parent of another child who was at the apartment about her concerns.
The emergency services were then alerted.
The files state that little Rehma passed away on January 16 at Boston's Children's Hospital after being found brain dead.