Detroit residents and city workers are on patrol as part of an annual anti-arson campaign for the pre-Halloween period that once saw an upsurge of fires.
A curfew took effect at 6 p.m. Tuesday for those 17 and under. The Angels' Night observance runs Tuesday through Thursday.
Police and fire officials say they won't release any figures on fire reports until after the three-day effort ends.
The program is a long-running response to what used to be known as Devil's Night, the day before Halloween.
In 1984, the city had more than 800 fires during the period. Last year, 93 fires were reported.