Dhananjay Kulkarni, deputy police commissioner in the western Indian city, said it was possible that the number of dead from drinking the illicit moonshine could reach three figures.
“Ninety people have now died,” he said. “More than 40 are being treated in hospital and the death toll may reach 100,” the commissioner added.
Victims first started to fall ill on Wednesday morning after consuming the illegal booze and new patients were still being admitted to hospital on Saturday, Kulkarni said.
Five people have so far been arrested for distributing and selling the alcohol in a slum in the suburb of Malad West, in the north of the city.
Eight police officers have also been suspended for “negligence” for allowing the sale to take place on their patch, Kulkarni said.
An investigation is taking place over whether high levels of methanol were present in the moonshine, often called “country liquor” in India.
Methanol, a highly toxic form of alcohol used as anti-freeze or fuel, is often added to bootleg liquor in India as a cheap and quick method of upping the alcohol content.
Unlicensed liquor is widely consumed across the country where it is sometimes sold for less than a dollar for a 25cl bottle, with deaths frequently reported.
It is rare however for such incidents to occur in a major city like Mumbai, with most cases taking place in poor, rural villages.
The latest incident is the worst case of its kind to be recorded in Mumbai since 2004 when around 100 people died.
In January, more than 31 people died near Lucknow in the northern state of Uttar Pradesh after drinking a lethal batch of home-brew.
And police arrested 12 people in October 2013 after more than three dozen villagers died from toxic liquor also in Uttar Pradesh.
In 2011 nearly 170 people died in the eastern state of West Bengal after drinking moonshine. -AFP