Public prosecutors in Brazil have begun legal action against South Korean electronics giant Samsung, alleging that it has been violating labour laws at its factory in the Amazon region.
Prosecutors accuse the company of making its employees work long, tiring shifts without sufficient breaks.
The prosecutors' office in the city of Manaus said one worker reported packing nearly 3,000 phones a day.
Samsung said it would take action "as soon as they are officially notified".
In a statement, the company said it would analyse the process and fully co-operate with the Brazilian authorities.
"We are committed to offering our collaborators around the world a work environment that ensures the highest standards when it comes to safety, health and well-being," the statement said.
The plant, located at the Manaus Free Trade zone, employs some 6,000 people.
A worker at the Amazonas state factory has only 32 seconds to fully assemble a mobile phone and 65 seconds to put together a television set, prosecutors allege.
In evidence given to prosecutors, employees say shifts can last 15 hours and some say they suffer from back ache and cramps as they are forced to stand for up to 10 hours a day.
The prosecutors' office is claiming more than 250m reais ($108m; £70m) in damages from the company for serious violations of labour legislation.
The legal suit was filed on Friday, but has only now been made public.