Mumbai on Saturday recorded 5,888 new COVID-19 cases, the lowest daily rise in infections since March 30.
Increased testing and isolation of patients alongwith the exodus of migrant labourers may have led to the decline, said an official.
Also, for the first time since April 12, when the city had reported 6,905 cases, the daily rise in infections in the country's financial capital fell below 7,000 on Saturday.
The caseload in the city stands at 6,22,109.
The city on March 30 had reported 4,758 COVID-19 cases, after which the figures had risen.
“Apart from increased testing and tracing and early isolation, the migration of over six lakh workers may have played a role in the reduction of numbers,” said a senior civic official.
Maharashtra Chief Minister Uddhav Thackeray had given several hints that the State was considering the reintroduction of lockdown-like measures which prompted migrant labourers to leave the city, he added.
The Central and Western Railways had run almost 500 special trains in last some weeks and most of them ran at full capacity.
The fall in cases on Saturday also brought down the positivity rate from 18% to 15% compared to the last week.
The overall growth rate of cases in the city is 1.26%.
On Saturday 8,549 patients were discharged after treatment, taking the tally of recoveries to 5,29,233.
“The strict lockdown-like measures further discouraged people from stepping out. The rising infections too must have persuaded some people to stay at home,” the official said.