In the week after nine people were shot dead at Emanuel AME Church in South Carolina, five churches with predominantly black congregations in five Southern states burned. Three of the fires were being investigated as arson.

The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives are working with local authorities to find those who set them.

“They’re being investigated to determine who is responsible and what motives are behind them,” FBI spokesman Paul Bresson told BuzzFeed News. “I’m not sure there is any reason to link them together at this point.”

The church fires come days after police say Dylann Roof, 21, shot and killed nine people during a prayer service on June 17 at Emanuel AME Church in Charleston, including the church’s pastor. Roof has been charged with nine counts of homicide and possession of a firearm.

Since the shooting, lawmakers and civil rights leaders have been focused on the backlash as people have been calling for the country to stop waving the Confederate flag. Now authorities are looking into the recent church fires at predominantly black churches, which the Southern Poverty Law Center, a civil rights group that tracks hate crimes, reports “may not be a coincidence.”

The first fire came late at night on June 21 when, authorities said, someone set fire to some hay bales just outside the College Hill Seventh Day Adventist in Knoxville, Tenn. The church sustained minor damage. A small church van was also burned.

“Horror, I was like, ‘Oh my gosh, what’s going on?’” Pastor Cleveland Hobdy III told WATE-TV.

D.J. Corcoran, a captain with the Knoxville Fire Department, told The Washington Post the fire was ruled an arson but not a hate crime. The incident is still under investigation.

Early June 23, God’s Power Church of Christ in Macon, Ga., was on fire. When firefighters arrived, the front doors were wired shut and they had to enter through a side door, the local newspaper the Telegraph reported.

“‘What’s the church doing on fire?’ That was my response to it,” Associate Pastor Jeanette Dudley told WMAZ-TV. “I just couldn’t believe it, and once I got here, I did. I cried. I cried for a little bit.”

Macon-Bibb County public information officer Chris Floore told The Post that the fire is being investigated as an arson, but it does not appear to be a hate crime at this time.

Early June 24, someone called 911 to report that Charlotte’s Briar Creek Road Baptist Church had been set ablaze.

“The Baptist church on Briar Creek Road right before Central, it’s on fire,” the caller told dispatchers. “It’s really big.”

It took more than 75 firefighters over an hour to get the fire under control and, by then, it had caused more than $250,000 worth of damage and demolished the church’s main building, The Post reported. Charlotte Fire Department Senior Investigator David Williams later said in a statement that a probe determined the fire “was intentionally set.”

Members of the church’s congregation held a Sunday service there to show resolve, according to the Charlotte Observer.

“I am standing on your shoulders,” the Rev. Rhonda Kinsey, the church’s pastor, told church-goers. “I am leaning on you. Part of our heart was consumed. Thank God, he is a heart-fixer.”

On June 26, the Glover Grove Baptist Church in Warrenville, S.C., burned down.

“Everything is gone — books, robes, all my pictures, all my degrees,” the Rev. Bobby Jean Jones told the Aiken Standard. “All the history is gone.”

“It’s all for the good, because God is in control and not me,” he added. “That’s why I’m calm, because I know who is in control, to tell you the truth. I’ve been knowing the Lord for a long time, and I know how he works. He will turn bad to good in a minute.”

Authorities said that in a statement no cause for the fire has been determined.

The Greater Miracle Temple Apostolic Holiness Church in Tallahasse also caught fire June 26, though authorities believe that fire was caused by an electrical wire. The incident is still under investigation.

No church-goers were injured in the fires.

Indeed, burning churches is nothing new. Such crimes go back to the Civil War era. But perhaps the most infamous case was in 1963 when four white supremacists bombed 16th Street Baptist Church in Birmingham, Ala. — an act the Rev. Martin Luther King Jr. called “one of the most vicious and tragic crimes ever perpetrated against humanity.”

The bombing killed four girls and injured others.

“From slavery and the days of Jim Crow through the civil rights movement and beyond, white supremacists have targeted the Black church because of its importance as a pillar of the Black community, the center for leadership and institution building, education, social and political development and organizing to fight oppression,” columnist David A. Love wrote for the Atlanta BlackStar. “Strike at the Black church, and you strike at the heart of Black American life.”

Amid last week’s fires, the Atlantic’s Emma Green wrote about the country’s dark history, noting that such incidents are “often association with racial violence: a highly visible attack on a core institution of the black community, often done at night, and often motivated by hate.”

Though the recent cases are not being investigated as hate crimes, motives remain unclear.

“But no matter why they happened,” Green wrote, “these fires are a troubling reminder of the vulnerability of our sacred institutions in the days following one of the most violent attacks on a church in recent memory.”

Correction: This story has been updated. A previous version stated six predominantly black churches caught fire. Only five had predominantly black congregations. The headline was changed to reflect that.