More than 40 people in northern India have been killed and a similar number are being treated in hospital after drinking illegally made alcohol during celebrations for a major religious festival.

Officials in the state of Uttar Pradesh initially said 32 people had died after drinking the alcohol during the festival, which took place last week.

Another 10 people have died in the past three days, they said yesterday, bringing the total to 42. The toll is expected to rise further as a number of those being treated are now said to be seriously ill.

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Police officer Arvind Sen told Associated Press that the victims bought pouches of the tainted liquor last Thursday from a shop in Adampur village, 180 miles south-east of the city of Lucknow, the state capital.

They started falling sick immediately after drinking the alcohol and were taken to local hospitals to be treated. By Friday night, 32 were reported to have died. Among those who died was a son of the shopkeeper who had sold the liquor. A number of those being treated in hospital have reportedly lost their sight.

The authorities in Uttar Pradesh, India’s most heavily populated and politically most important state, have launched an investigation into what happened and several officials, including excise officers and police, have reportedly been suspended. The state’s chief minister, Akhilesh Yadav will likely wait for the investigation to be completed before deciding what other measures to take.

Such incidents are depressingly common across rural and small-town India, where illegally made alcohol is easily available and widely advertised. In 2011, more than 140 people died in similar circumstances in a village near the city of Kolkata and in 2008 around 180 lost their lives in an incident in the southern city of Bangalore.

Reports suggest there are good profits to be made by the manufacture and sale of so-called country liquor, or “sharab”. But those involved in the production frequently mix their product with other chemicals, such as methanol. The mixing is done to make the product more potent but additives can cause blindness and death.

Despite this, sales of illegal liquor persist because of its low cost; the hooch costs just a third of the price of even the cheapest liquor sold in government-sanctioned shops and is therefore affordable to people such as labourers and farm workers. Reports suggest as much as two-thirds of all alcohol consumed in India is illegally-produced.

Two years ago the state of Gujarat passed a law that introduced the death penalty for those convicted of producing illegal liquor that was responsible for people dying. The law was introduced following an incident in the city of Ahmedabad in 2009 in which 157 people died.

Around 30 people have been arrested as part of the investigation into what happened in Uttar Pradesh, including the shopkeeper whose son was among the victims. People had been drinking the illegal liquor as part of celebrations for the Hindu Dussehra festival.