A historic black church just north of Charleston, South Carolina was on fire Tuesday night, making it the sixth predominantly black church in the United States to burn in the less than two weeks since a white supremacist massacred nine people, all of them African-American, at their parish.

This is not the first time the Mount Zion African Methodist Episcopal church in Greeleyville, a town of 400 people, has caught ablaze. In 1995 the Klu Klux Klan burned it down, almost 20 years to the date before Tuesday's inferno.

It is believed that no one was inside at the time of Tuesday's fire. The chief of the South Carolina Enforcement Division, Mark Keel, told the New York Times that it was too early to determine cause of the blaze.

Many suspect that the string of fires is part of an anti-black backlash in the wake of the white supremacist killings at Charleston's Emanuel African Methodist Episcopal church on June 17.

The NAACP said in a tweet on Tuesday that "State Conferences and Units are now alerting black churches to take necessary precautions."

Meanwhile, the hashtag #WhoIsBurningBlackChurches has been trending on Twitter:

#WhoIsBurningBlackChurches Tweets

A report released by the Southern Poverty Law Center before Tuesday identified other fires that "damaged or destroyed" majority black churches in five states in the south since June 21—just days after the Charleston killings. According to SPLC's count, at the following three churches, the fires are believed by authorities to have been caused by arson:

• College Hills Seventh Day Adventist Church in Knoxville, Tennessee.
• God's Power Church of Christ in Macon, Georgia.
• Briar Creek Baptist Church in Charlotte, North Carolina.

The other predominantly black churches that burned are:

• Glover Grover Baptist Church, in Warrenville, South Carolina—cause unknown.
• Greater Miracle Apostolic Holiness Church in Tallahassee, Florida—authorities suspect electrical lines, but investigation ongoing.

The SPLC said that at least some of the fires constitute "suspicious and possible hate crimes." The organization noted the blazes "occurred at a time when there is increasing public pressure to remove the Confederate flag—one of the last hallmarks of white superiority—from government buildings and public places as well as banning assorted Confederate flag merchandise sold in retails stores and online."

Buzzfeed reported late last week that the Federal Bureau of Investigation and the Bureau of Alcohol, Tobacco, Firearms and Explosives are working with local authorities to investigate the fires.

Amid a growing, nationwide movement against institutional racism and killings, under the banner of Black Lives Matter, many say that the church burnings emphasize the need to address institutional anti-black terror in America.

Writer David A. Love wrote in the Atlanta Black Star last week that "the Black church always has been under attack because Black people always were under attack."

Love continued: "We should remember that Emanuel AME was once burned down because of its ties to the Denmark Vesey slave rebellion in 1822. At a time of increased assaults against Black people in the streets, in the courts and the state house, in police custody and in all realms and spheres of life, the Black church is once again under assault."