( CNN ) -- Authorities in Ecuador have banned alcohol sales in an emergency measure to stop contaminated drinks from reaching consumers after at least 21 people died . Officials announced the 72-hour national dry law Sunday after detecting alcohol poisoning cases in several parts of the country . Hospitals treated more than 100 people who fell ill after drinking bootleg liquor over the past week , the country 's government said , and at least 21 people died as a result of apparent poisoning . Investigators determined that the liquor contained methanol -- an industrial-grade alcohol not intended for human consumption , Ecuador 's Public Health Ministry said . `` It is a potent poison that can in small quantities , including a quarter of a cup , cause the death of the individual that consumes it , '' Health Minister David Chiriboga told reporters . The liquor was sold in unlabeled bottles , with no indication of its contents or where it originated , Los Rios Gov . Jesus Narvaez told CNN affiliate Ecuavisa . Doctors in the province first began seeing cases of alcohol poisoning last Tuesday , Ecuador 's government said . By Sunday , 103 patients showing symptoms had showed up at local hospitals . Authorities in Los Rios implemented a curfew , shut down bars and confiscated hundreds of unlabeled bottles containing bootleg alcohol , Ecuavisa reported . The liquor `` was massively consumed '' during a festival in the town of Urdaneta , Los Rios , Ecuador 's government said in a statement . The 21 patients who died all haled from Los Rios , but similar poisoning cases have also been reported in at least four other areas , the government said . Authorities have arrested the liquor seller and continue investigating , police said .
NEW : Health minister : The contaminated alcohol contained a `` potent poison '' NEW : A province governor says the alcohol came in unlabeled bottles . Officials announce a 72-hour national dry law . Score: 6