The reward for information leading to an arrest in the possible arson cases was increased from an initial $2,000 to $9,000, St. Louis Police Officers’ Association spokesman Jeff Roorda confirmed to Al Jazeera Wednesday.

St. Louis police Chief Sam Dotson told the St. Louis Post-Dispatch Tuesday that the churches damaged by suspicious fires from Oct. 8 through Oct. 18 vary denominationally and are within a few miles of each other.

Four are on St. Louis' north side, and two are in nearby Jennings.

Five of the churches have predominantly black congregations, and one congregation is racially mixed. In each case, the front door of the church was set on fire, but the damage varied from superficial at one church to the near destruction of another.

St. Louis and federal authorities, including personnel from the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, are investigating the fires. They are trying to determine whether the fires were set to target religion or race or both. St. Louis Fire Capt. Garon Mosby has said the possibility that the fires could be hate crimes based on religion or race "is part of the dynamic" of the investigation.

The area is still reeling from the shooting death last year of 18-year-old Michael Brown, who was black, by police officer Darren Wilson, who is white, in Ferguson, Missouri and a grand jury's subsequent decision not to charge Wilson. Brown was unarmed when he was shot by Wilson, and the case spurred the national Black Lives Matter movement scrutinizing police treatment of minorities.

Al Jazeera and The Associated Press