Door-to-door screening is underway in Mumbai's poor neighbourhoods to identify coronavirus clusters.
India topped half a million cases of coronavirus last week and the country has ramped up testing, conducting more than 170,000 tests on Sunday.
New Delhi and Mumbai have become the worst-hit cities in India, with police in Mumbai re-imposing lockdown in zones where rates of infection are higher.
India has the fourth-highest number of coronavirus cases globally behind the United States, Brazil and Russia. It has recorded a total of 549,986 and more than 16,500 deaths.
But the number of infections is thought to be far higher because many people have not been tested, and studies suggest people can be infected with the virus without symptoms.
