Rahul Gandhi visited the NTPC plant in Uttar Pradesh's Raebareli on Thursday.
Arvind Kumar, a principal secretary, said some of the severely injured had been taken to a hospital in the state capital Lucknow. "Blockages in the flue gas pipe in a unit led to the blast. Hot flue gases and steam let out by the blast severely injured several workers," Sanjay Kumar Khatri, the top government official of Raebareli district where the plant is located, told Reuters on Thursday.
"A magisterial inquiry has been initiated. This two-member technical team will submit findings within seven days," Mr Khatri said.
In a statement, the NHRC said an investigation was needed to ascertain whether negligence or errors had caused the explosion, and asked the state government to submit a detailed report within six weeks.
The boiler pipe burst in a 500 MW power unit in the NTPC plant that started operating in March.
Senior state police official Anand Kumar said on Wednesday ash had piled up in the furnace beneath the boiler, which led to a build-up of pressure resulting in the explosion.
The Raebareli Lok Sabha seat is represented by his mother, Congress president Sonia Gandhi. Mr Gandhi joined other leaders of the opposition in demanding a judicial inquiry, suggesting that facts could be concealed.