Irreversible multiple organ failure and acute respiratory distress syndrome are believed to have caused his dealth, doctors said.
Mahajan's body was taken to GT Hospital for a post-mortem.
BJP leaders have expressed shock over the death saying it was not only a big blow to the party but also to the nation as a whole.
"I am shocked. It's a great loss not just for the BJP but for the country as a whole as you will not have a leader of his dynamism, energy and promise," Yashwant Sinha, senior party leader and former external affairs minister, said.
Describing Mahajan as an "elder brother", Ravishankar Prasad, spokesman for the BJP, said he was an inspiration to the young generation of BJP leaders.
The Congress party too expressed deep grief over Pramod Mahajan, whom it described as one of the most competent ministers, a very
good organiser and an able politician who played an important
role in Indian politics.
