"Our officials took Singh into custody after he reached Bangalore from Singapore where he had gone for heart treatment," a Central Bureau of Investigation official told IANS here.
Singh was whisked away to the agency's office in the northern suburb of the city. A warrant was pending against him from the CBI's special court under the Prevention of Corruption Act and the Indian Penal Code (IPC).
"We will produced him in our special court later in the day after medical examination to seek his custody for further interrogation," the official said on the condition of anonymity.
Singh was elected from Vijayanagara in the mineral-rich Bellary district, about 330 km from Bangalore, on Bharatiya Janata Party (BJP) ticket in the May election.
Singh was tourism minister for eight months from September 2012 to May 2013 during the BJP's third government led by Jagadish Shettar.
According to the FIR (first information report) the CBI had filed, Singh's mining firm (Vaishnavi Minerals) had allegedly supplied around 1.3 lakh tonnes of the illegally extracted iron ore for export from the port between January 2009 and May 2010 when the BJP ruled the state.
Singh left for Singapore Sep 25 after filing an application for anticipatory bail in the CBI court.
Singh is the fourth lawmaker to be arrested in the case after T.S. Suresh Babu of BSR regional party from Kampli and B. Nagendra from Kudligi (independent) in Bellary district and Satish Sail from Karwar (independent) in the coastal Uttara Kannda district.
They were taken into custody during the last one month for their alleged involvement in the iron ore export scam.