The number of people killed by a batch of bootleg raki, Turkey’s national drink, has risen to 25 after a man died of alcohol poisoning in hospital on Monday, the Istanbul Health Directorate said on Tuesday.

At least six people remain seriously ill in Istanbul, Turkey’s largest city, where all but one of the deaths have occurred. Some have been linked to raki consumed at a restaurant, while other drinkers were poisoned after buying the strong, aniseed-flavoured spirit at grocery stores.

Police suspect the lethal batch, which according to news reports contained between 57 and 97 percent methyl alcohol, compared with 0.15 percent for genuine raki, came from an underground distillery in Istanbul.

Since the first deaths in February, dozens of people have been detained in raids around the country.

The U.S. Embassy in Ankara has warned its citizens that drinking raki, nicknamed “lion’s milk,” could cause illness or death. It said some 500,000 bottles and tax holograms stolen from a legal distillery had been used to authenticate the fake liquor, which was sold to stores and restaurants.

The largest raki maker, Mey Icki, recalled up to five million bottles of the drink last week. Turkey’s government, led by former Islamists, has rejected suggestions that recent tax hikes have encouraged a boom in illegal liquor factories.