The deaths happened mainly in two villages in the eastern state of Bihar, where the sale and consumption of liquor are prohibited.

Such bans are in force in several Indian states, driving a thriving black market for cheap alcohol made in unregulated backstreet distilleries that kills hundreds of people every year.

In the latest incident, men in Saran district began vomiting on Tuesday before their condition deteriorated.

Three died on the way to hospital and others died while being treated on Wednesday and Thursday, with local media reports putting the toll at 31.

Hospital chief Sagar Dulal Sinha said 22 post-mortem examinations had been conducted so far.

Senior police officer Santosh Kumar said authorities had cracked down on illicit alcohol shops in the area.

“We have arrested over a dozen liquor traders and detained some others,” Kumar told AFP.

Of the estimated five billion litres of alcohol drunk every year in the country, around 40 percent is illegally produced, according to the International Spirits and Wine Association of India.

Illicit liquor is often spiked with methanol to increase its potency. If ingested, methanol can cause blindness, liver damage and death.

In July, 42 people died in the western state of Gujarat after drinking bootleg booze.

And last year, about 100 people died in the northern state of Punjab in a similar incident.