Assam Chief Minister Tarun Gogoi on Sunday questioned the source of BJP's poll funding in the recent assembly elections during which, he said, the party had "spent money like water" while campaigning."The amount of money involved in the BJP poll campaigning raises strong doubt on its source of funding. The party spent money like water and such a lavish campaign is unimaginable without strong corporate backing," Gogoi said in a statement here.The chief minister said it was for the first time in Assam that the union finance minister and external affairs minister visited the state and held meetings with businessmen. Gogoi said the huge amount spent on campaigning must have come from black money pumped in by sources best known to the Bharatiya Janata Party."Will someone give so much money without benefits in return? The reason behind (this largesse) is anybody's guess...."