Stores and schools throughout Rio de Janeiro shut down Monday, apparently in response to threats by the city's most powerful drug gang. Police have detained 19 people in connection with the threats, which spread panic throughout the city.

Normally busy streets had little traffic Monday, as stores shut down for at least part of the day apparently in response to direct threats, or rumors of threats from drug traffickers. Even upscale neighborhoods in this scenic city were affected, while schools and universities sent their students and teachers home.

Media reports said the shutdown order came from a drug gang linked to Luiz Fernando da Costa, who, despite being jailed, remains the city's most powerful drug lord. According to reports, da Costa's supporters are demanding he receive better treatment in prison.

Authorities deployed thousands of police on Rio's streets to restore calm, and persuade storeowners to reopen. Police also made a series of arrests of those suspected of making the threats.

Drug gangs, which control Rio's shantytowns, often order shutdowns of neighborhood stores and schools when a gang member is arrested or killed. But Monday's shutdowns were much more widespread, and affected large parts of the city.