Thousands of volunteers are preparing to join city workers in patrolling Detroit streets as part of the annual three-day Angels' Night anti-arson campaign.
The observance begins Sunday and runs through Tuesday night.
Residents also are asked to keep porch lights on and report any suspicious activities around vacant structures.
The day before Halloween had historically been a time of mischief and called Devil's Night in Detroit.
Vacant houses began to be torched in the 1980s. The city had more than 800 fires during the Halloween period in 1984.
The city reported 59 fires during last year's Angels' Night campaign. Fewer than two dozen were considered suspicious. There were 52 fires in 2015.
This year, the city and community leaders are expanding the number of parties, trick-or-treating and other Halloween-themed activities.