A mass alcohol poisoning in Kaunas, Lithuania has resulted in the deaths of at least 16 people shortly after being taken to the hospital.

An unidentified, 63-year-old woman was arrested and charged last week under suspicions of negligent deprivation of life, officials told Lithuanian press. This was not the woman’s first offense with dangerous alcoholic beverages, as she had been arrested once before on prior convictions for illegally trafficking domestic alcohol and ethyl alcohol.

Searching the woman’s home, authorities in Lithuania found multiple containers filled with unknown liquids, which were confiscated for further inspection.

The victims, taken to hospitals all around the area of Kaunas, Lithuania, died shortly after arriving, all between 30 and 60 years old.

According to LRT English, prosecutor Auksė Lipkevičienė from the Kaunas Regional Prosecutor’s Office informed reporters that they are, “currently carrying out 17 pre-trial investigations, including 16 on the cause of death and another one on negligent deprivation of life.”

“Since the beginning of this month, a total of 16 men and women of various ages have died in Kaunas hospitals, possibly from the same alcohol surrogate, most of them residents of the same district,” Lipkevičienė said. “Another 2 people are currently being treated by doctors. It is not ruled out that the number of people intoxicated with alcohol may increase further.”

What also remains a mystery is the motive. Authorities are unsure whether the homemade alcohol poisoning was the result of an accident or a planned mass murder.

According to Newsweek, toxicologist Jonas Šurkus, a doctor at the nearby Nephrology Kaunas Clinic, told local Lithuanian publication Apollo.lv that, “alcohol poisoning with ethanol is usually not severe.”

It is only when mixed with methanol, which Šurkus believes is what happened to the mass alcohol poisoning victims in this particular case, that it leads to becoming fatal. “Surviving patients may be left with irreversible organ damage,” Šurkus told officials, “such as kidney failure or blindness.”

Methanol is a “very cunning alcohol,” Šurkus said, “the most poisonous surrogate of alcohol.”

Ever since the late 2000s, alcohol in Lithuania has actually been very strictly regulated. After a report released by the World Health Organization (WHO) ranked Lithuania as one of the countries with the highest alcohol consumption levels per capita, the country began drafting policy that would limit not only where you could buy alcohol, but also who could consume it.

By 2016, alcohol-related measures had made a “total ban of alcohol advertisement in the media, internet, and billboards, etc.,” common throughout the country. Lithuanian citizens were also no longer allowed to carry alcohol in kiosks and gas stations, and raised the drinking age from 18 to 20 years old. Lithuania also imposed a “major increase in excise tax.”

The World Health Organization reported that the measures in 2016 brought the rate of alcohol-attributable years of life lost in the European Union down by 20% since 2010, when Lithuania held the highest rate.

In the United States, the Center for Disease Control and Prevention (CDC) reported that, “There are 2,200 alcohol poisoning deaths each year.” Similar to the victims of the Lithuanian alcohol mystery, the CDC said that 76% of alcohol poisoning deaths are among adults ages 35 to 64 in the U.S. as well.

“Very high levels of alcohol in the body can shutdown critical areas of the brain that control breathing, heart rate, and body temperature,” the CDC explained, which often results in death.

The Lithuanian mass alcohol poisoning follows other scary deaths in the world this week, such as a child in California who picked up an incredibly rare brain-eating amoeba while swimming in a lake with his family this past summer.