The Justice Department is investigating a rash of fires at black churches to determine whether the cause is arson and hate crimes.

"The federal law enforcement team of ATF, FBI, the Civil Rights Division and U.S. Attorneys' Offices are actively investigating several church fires across five states that have occurred over the past two weeks," Justice Department spokeswoman Melanie Newman stated on Thursday.

"Preliminary investigations indicate that two of the fires were started by natural causes and one was the result of an electrical fire," Newman continued. "All of the fires remain under active investigation and … the investigations have not revealed any potential links between the fires."

A civil rights organization called Thursday for an investigation and the largest union of federal workers said it was concerned about the incidents.

"These tragedies will only end with accountability, and accountability is only possible through comprehensive investigations and effective prosecutions," said Rashad Robinson, executive director of advocacy group ColorofChange.org.

Seven black churches have been set ablaze under questionable circumstances and at least three black women pastors have received death threats since Dylann Roof shot and killed nine people at a black church in Charleston, S.C. last month, according to ColorofChage.

"In the context of increased white supremacist attacks and the ongoing history of racial violence targeting black churches, the Department of Justice and Attorney General Loretta Lynch must take definitive action to thoroughly investigate the recent church burnings and death threats targeting black pastors as hate crimes and domestic terrorism," said Robinson, whose group advocates for the African-American community.

Robinson said that a 1996 church-arson task force "led to more than 832 investigations into church burnings and increased the number of prosecutions."

"Make no mistake, the person or persons setting these fires is just as guilty of terrorism as the young man who gunned down those nine parishioners at Emanuel," the American Federation of Government Employees stated. "As leaders in the labor movement, we stand in solidarity with disadvantaged people everywhere who are fighting for equality, justice and dignity at work, at home and in their communities."

The NAACP also recently issued a statement of concern about the fires.

"The spike in church burnings in Southern states over the past few days requires our collective attention," the oldest black civil-rights organization stated. "When nine students of scripture lose their lives in a house worship, we cannot to turn a blind eye to any incident."

"As we wait for authorities to conduct their investigations, the NAACP and our state conferences across the country will remain vigilant and work with local churches and local law enforcement to ensure that all are taking the necessary precautions to ensure the safety of every parishioner," the statement read.