A team from the Central Bureau of Investigation (CBI) on Monday once again visited the flat of late actor Sushant Singh Rajput, while another team continued grilling Rhea Chakraborty, her brother Showik and Sushant's former manager Shruti Modi.Rhea and Showik arrived at the DRDO guest house where the CBI team is staying for the fourth consecutive day, while Shruti Modi arrived one and a half hours later.Sushant's flatmate Siddharth Pithani also arrived at the DRDO guest house for questioning.Sources in the agency said that Rhea is being questioned about her break-up with Sushant, when did she come to know about the death of the actor and how she managed to enter the mortuary of Cooper hospital.Rhea is also being questioned about the WhatsApp chats where she was talking about drugs and relations with filmmaker Sandeep Ssingh and Shruti Modi.She has been questioned by the CBI for over 25 hours in the last three days. On Friday she was questioned for over 10 hours, seven hours on Saturday and eight hours on Sunday.Following the Supreme Court's order, the CBI arrived in Mumbai after they registered a case on the Centre's orders on August 6 following the complaint by Sushant's father K.K. Singh in a Patna police station on July 25.The CBI has till date questioned Sushant's flatmate Siddharth Pithani, personal staff Neeraj Singh, Dipesh Sawant and others.The CBI team has already visited Cooper hospital twice and the Waterstone resort where Sushant had stayed for some time besides Sushant's Bandra flat, where he was found dead on June 14.