Police also discovered a blood-stained cricket bat in the Blade Runner’s mansion in Pretoria, South Africa — and evidence of heavy drinking before the 3am shooting.
Cops are now probing a theory that Pistorius may have blasted Reeva in an explosion of fury caused by the performance-boosting steroids.
They are investigating whether murder suspect Pistorius was in the grip of “roid rage” — a side-effect of high doses of the outlawed drugs.
Officers who searched the 26-year-old’s home after lover Reeva was killed in the bathroom are said to have found steroids. Blood samples taken from Pistorius are being tested for the drugs.
A source close to the investigation said: “Steroid drugs were found at Pistorius’s home together with evidence of heavy drinking. That’s why police have specifically ordered that he be tested for steroids.”
Model Reeva was killed by 9mm pistol shots fired through the locked bathroom door at around 3am on Valentine’s Day.
She was hit in the head and body four times in total. But police now believe the first shot was fired at her in the master bedroom — hitting her hip as she fled to the bathroom.
Wounds to the top of her head suggest that as she sat doubled up in pain on the toilet she was hit three more times by bullets that ripped through the door.
Experts say she may have been covering her head protectively with her hands, which explains the bullet wounds to her finger and arm.
A blood-stained cricket bat was found at the home in Pretoria, South Africa — and Reeva, 29, appeared to have skull “crush injuries”. Tests will establish whether she was injured by the bat before being shot.
Police will also examine the theory she used the bat to defend herself or that Pistorius used it to smash his way into the bathroom.
The Paralympics hero denies murder. He is expected to claim he fired after mistaking her for an intruder.
His legal team are reported to be claiming he forgot Reeva was staying the night and mistook her for a burglar when he was woken by a noise.
Phone records are also being checked after South African reports suggested Reeva got a late-night text from South African rugby star Francois Hougaard, a pal of Pistorius’s.
Detectives believe Pistorius may have been angry at the text.
Handsome Hougaard, 24, was close to Reeva before she paired up with Pistorius in November.
Sources said Pistorius was unhappy they remained friends. Hougaard has insisted the “whole sad ordeal” of Reeva’s death had nothing to do with him.
A woman neighbour whom Pistorius called after the shooting will be a key witness.
She rushed out to see the athlete carrying Reeva’s blood-covered body. She told police he was in a state of “delirium” and said he mistook his lover for an intruder.
Pistorius’s best pal Justin Divaris told how the sobbing athlete rang him to say: “I’ve killed my baba. God take me away.” Justin said Pistorius sat in his garage weeping into the phone as police sealed off his house.
He added: “Oscar called at 3.55am saying Reeva had been shot.
“I said, ‘What are you talking about? I don’t understand’.
“He then repeated, ‘There has been a terrible accident, I shot Reeva’.”
Police arrived at the mansion — which has five reception rooms, a Roman-themed roof pool and three garages — and followed a trail of Reeva’s blood inside.
They found her overnight bag and an iPad on the bedroom floor. The holster for Pistorius’s Taurus pistol was at the side of the bed.
The bedclothes were crumpled, suggesting it had been slept in. A bullet cartridge was found in the bedroom — leading to the theory that the initial shot was fired there.
Police also have CCTV showing Reeva arriving at the house on the Silver Woods estate at 6pm.
Neighbours told of hearing shouts and screams on Wednesday and early on Thursday.
Pistorius was yesterday visited in his police cell by brother Carl, sister Aimee and other family members — and urged them to keep Reeva’s relatives in their thoughts.
Carl tweeted: “Praying unceasingly 4 Reeva’s family like my brother asked. Praying 4 my brother.” Last night Reeva’s mum June, 66, sobbed as she asked: “Why would he kill my angel?”
June, speaking publicly about the horror for the first time, added: “She was our golden angel and had so much love to give. I don’t understand. Why would he do it?”
The athlete’s agent Peet van Zyl said: “After the tragic circumstances, we can only give Oscar our support.”
Olympian Pistorius’s arrest shocked his fans. They will be almost as stunned by the steroid claims.
The drugs, which boost muscle growth by raising levels of male hormone testosterone, are banned in sport. They can cause liver and heart damage — as well as the aggressive behaviour known as “roid rage”.