SAO PAULO, BRAZIL -- Police killed 13 suspected gang members in a shootout outside a prison in South America's largest city on Monday as authorities foiled an alleged plot to attack prison officers.

The violence came six weeks after imprisoned gang leaders allegedly ordered attacks against police across the city and Sao Paulo state, sparking a weeklong wave of violence that left nearly 200 police, prison officers, suspected criminals and jail inmates dead.

There were no signs that Monday's violence was spreading or having any impact on daily life in Sao Paulo, a metropolis of 18 million.

Although police were on high alert, Sao Paulo state Gov. Claudio Lembo said authorities did not expect a return of widespread violence.