Sadhvi Pragya Singh Thakur has been arrested by Madhya Pradesh Police in connection with the murder of Sunil Joshi, a suspect in the Samjhauta Express blast case. He was killed at Dewas in December 2007. Sadhvi Pragya is also key accused in 2008 Malegaon blast case.Reports from Mumbai say, the MP police had earlier moved an application in the special MCOCA court. Special Public Prosecutor Rohini Salian said after taking the court's permission they placed Sadhvi under arrest in the Sunil Joshi murder case.Pragya Singh, main accused in 2008 Malegaon blast case in Maharashtra, has been undergoing treatment in J J hospital there.Sixty-eight people were killed when bombs went off in two coaches of Samjhauta Express on February 18, 2007 at Diwana near Panipat, 80 km north of Delhi.