ST. LOUIS — Arsons at six predominantly black churches in this metropolitan area in recent days are believed to be connected, fire officials said on Tuesday.

The fires, all set in the entryway or door of a church, have taken place here since Oct. 8, the authorities said. The latest blaze was discovered on Sunday morning by those arriving for a service at Ebenezer Lutheran Church.

The arsons have occurred at churches with mostly black memberships and in mostly black neighborhoods in a region that has wrestled with issues of race, but the authorities said they did not know whether race had played a role.

Officials have offered a $2,000 reward for information that leads to the arrest of those responsible, and several agencies, including the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, are investigating.