A senior minister said in Mumbai today that Mumbai's civic body has claimed a 'significant decline' in the number of malaria cases since the last four days.Rural development minister Jayant Patil, who is also the guardian minister of the island city district, told reporters at Mantralaya in Mumbai today that the BMC has said that since August one, there has been a significant reduction in the number of incoming malaria cases in city hospitals. To a query, the minister denied having ever said that migrant workers at the plethora of construction sites in the megalopolis were to blame for rise in malaria cases.There are 2500 construction sites in Mumbai.