The incident took place in Kanpur Development Authority colony in the afternoon, when top floors of the seven-storey under-construction building started falling, Modak said.
Railways Ministry spokesperson Anil Saxena said several people have been rushed to nearby hospitals with injuries, and the casualties may go up.
The IMD has predicted heavy rainfall over Karnataka and Kerala for the next few days.
Even as nature's fury is causing multitude of disasters in Uttarakhand and Himachal Pradesh, the Centre is yet to appoint head of the specialised 10,000- personnel strong NDRF, the mainstay for disaster mitigation and rescue operations in the country.
Prime Minister Narendra Modi spoke to Chief Minister Sarbananda Sonowal over phone and discussed about the prevailing condition on Monday.
The fire department said they received a call around 4.23 am about a fire in the factory at Udoh Nagar area after which seven fire tenders were rushed to the spot, the official said.
Taking note of large-scale deaths because of the heat wave in various parts of country, Prime Minister Manmohan Singh has asked a Group of Ministers to discuss and decide on its inclusion as natural calamity.
Centre releases Rs1,712cr to TN, Rs 1,234cr to Karnataka for drought.
In Assam, nearly 27.80 lakh people across 26 districts have been affected by the deluge. The deaths were reported from the Barpeta, Kokrajhar and Morigaon districts. The death toll due to floods and landslides this year has risen to 122.