Sinh has been admitted to the NRS hospital after he complained of stomach pain, doctors in the hospital said.
Sinh was arrested in connection with Saradha Realty case on charges of criminal conspiracy and cheating.
He had been earlier questioned by the Enforcement Directorate too in connection with Saradha scam in Delhi.
Sinh was questioned for more than seven hours by the investigating agency, a CBI spokesperson said.
"I do not know Sudipto Sen," he said.
The former Congress MP from Assam said he had "submitted money to the Shyamal Sen commission", formed soon after the Saradha scam broke, to repay the investors.