Police are raiding illegal distilleries in eastern India, where the number of people who have died after drinking toxic home-brewed liquor has reached 170.

At least 90 others in the Sangrampur area of West Bengal state remain critically ill.

Local officials say 12 people have been arrested so far for allegedly making and distributing the tainted liquor, but police on Friday were still looking for the kingpin of the operation.

Most of the victims were day laborers and other poor workers who bought cheap alcohol from bootleggers late Tuesday.

Authorities were also working to determine the chemical ingredients in the liquor, with officials saying that methanol had been detected in at least some of the victims.

West Bengal Chief Minister Mamata Banerjee has ordered an investigation into the liquor deaths and vowed to crack down on illegal liquor brewers, who often spike their alcohol with chemicals to increase potency.

Villagers angered by the deaths have also ransacked local breweries suspected of selling the tainted liquor.

Alcohol poisoning kills hundreds of people in India every year.