Arson investigators in St. Louis are trying to determine who burned down 5 black churches in the St. Louis/Ferguson area.

Investigators say someone set fire to the New Life Missionary Baptist Church on Saturday. It was the fifth black church to go up in flames this month. A sixth church, which has a mixed-race congregation, was set ablaze on Sunday.

Nearby Ferguson, MO., has been a hotbed of civil unrest since the police shooting of unarmed teenager Michael Brown last year.

Authorities refuse to link the torched churches to the ongoing racial tension in Ferguson.

From The Washington Post:

Authorities said all of them were intentionally set. Investigators are now trying to find the culprit as well as a motive to see whether it might have to do with race or religion.

“We believe that this fire-setting activity is meant to send a message,” Bureau of Alcohol, Tobacco, Firearms and Explosives said in a statement. “We believe this activity may be the result of stress experienced in the subject’s life.”

Parishioners have called the arson attacks “destructive” and “disappointing,” and say it “disturbs the heart.”