Oscar Pistorius' girlfriend Reeva Steenkamp's text messages to a South African rugby player is set to play a key to investigations into her death as banned steroids reportedly found in the Paralympic star's home. South African police are believed to be checking SMS and text messages from the slain model's iPad and mobile phone to try to establish a motive for her death, News.com.au reports. Steenkamp was believed to be in a close friendship with rugby star Francois Hougaard when she was killed. Pistorius has been charged with the Valentine's Day murder of 29-year-old Steenkamp who was shot dead at his luxury Pretoria. Detectives are also investigating whether the famed Blade Runner sprint star was overcome with aggression, or 'roid rage', a side effect of the banned drugs, a British tabloid reported. An unnamed police officer said the drugs and syringes were found shortly after Pistorius' house was sealed off, adding crime scene investigators were searching a room linked to the crime when they found them. The officer added along with the drugs and syringes, officers seized the victim's iPad and mobile phones, adding they are being analysed by computer data experts, who have retrieved important information, including SMSes and social-media site messages, which are potential keys in establishing the motive. Reports in South Africa have linked Steenkamp with Hougaard, who is also friends with Pistorius. Investigators are looking into whether Steenkamp's friendship with Hougaard may have sparked the rows, which were heard in the hours leading up to the shooting, the paper said. The pair has been friends for several years and had reportedly dated in the past. Hougaard, on his Twitter account, reposted a photo of himself with Steenkamp and two other friends, which read: "Happier times with special people. We all miss u so much Reevs. Hougaard's agent Lorinda Voges said he was in mourning for his friend, the paper added.