Last weekend, Pintu Kumar, a farmhand in northern India, went to a friend’s memorial service.

On the way back to his village, he bought dozens of small plastic pouches of homemade alcohol. They weren’t labeled — they usually aren’t — but the alcohol was incredibly strong and cheap, at about 40 cents per pouch.

It was also unusually milky in color and smelled like diesel fuel. But that didn’t stop Mr. Kumar from tearing holes in a couple of pouches and sharing them with his friends.

Then tragedy struck.

“All of them died,” said Bimlesh Kumar, a resident of the same village. “The bodies were scattered on the ground as if a massacre had been committed.”

In the past few days, a poisonous batch of illegal homemade alcohol has killed as many as 100 people in northern India. The deaths, which have rattled the country and become front-page news, prompted the authorities to crack down on underground brewers, arresting more than 3,000 suspects and seizing tens of thousands of gallons of illicit alcohol.