были арестованы

were arrested

→ быть
phrase Rare #33,155
were arrested Past passive form used for plural subjects, or for formal singular contexts with implied plurality in news reports and official language.
RU: Вчера два человека были арестованы.
EN: Yesterday, two people were arrested.

Тысячи людей там были арестованы.

Thousands of people were arrested there.

Ни Том, ни Мэри не были арестованы.

Neither Tom nor Mary were arrested.