A case has been registered against two shop owners after a portion of a four-storey residential building collapsed in Mumbai on Tuesday evening.According to the police, Yunus Kasam Memon and Irfan Yusuf Memon, who own a shop of mobile handset covers, had allegedly added a staircase without seeking permission. This led to collapse of the building 'Yusuf Manzil' at Lamington Road.Meanwhile, an 85-year-old woman, who was seriously injured in the collapse, died on Tuesday.