RIO DE JANEIRO, Aug. 30 (Xinhua) -- Brazilian police detained 37 people on Thursday following an operation in Rio de Janeiro against a group of police who were extorting alleged criminals.

At a press conference, Rio de Janeiro's secretary of public safety said that 21 civil police officers, four military personnel, a firefighter and a prison officer, among others, were detained during the operation.

According to the authorities, the group would demand money from vendors selling counterfeit goods, street vendors selling gas, and vendors who did not have permits.

The group used a band of informants who helped to locate the vendors without permits.

The extortionists, according to the authorities, would threaten and "physically assault" their victims and sometimes take the goods and resell them.

The leader of the group was a commissioner with the civil police in Rio de Janeiro, and his righthand man was the chief of investigations.