WICHITA — A federal terrorism task force is investigating after mail laced with a dangerous toxin was sent to a Sedgwick County government office, causing coughing and skin irritation for four employees and forcing several to undergo decontamination.

The Sedgwick County Finance Department in the county courthouse received the certified letter on Monday.

The three-page letter was coated in a white powder, and two employees who handled the letter experienced symptoms of coughing and skin irritation, Sedgwick County Manager Tom Stolz told the Wichita Eagle. Others were also affected.

A finance division employee who was exposed was treated at a hospital and is now recovering at home, the Sedgwick County Sheriff’s Office said Tuesday in a news release. Three other county employees are experiencing minor symptoms but continue to work, the sheriff’s office said.

The FBI’s Joint Terrorism Task Force determined that the substance is diaminotoluene, a chemical used in dye making, Stolz said. It is highly toxic and potentially fatal if enough is inhaled, swallowed or absorbed through the skin.

Three other finance employees, two courthouse police officers and two sheriff’s deputies underwent decontamination as a precaution, the sheriff’s office said.

The letter purported to come from the “Moorish Nationale Republic Federale Gobernmete – Societas Republic ea al Maurikanos,” the sheriff’s office said. Stolz said the origin of the letter remains under investigation.

The Southern Poverty Law Center says the Moorish nationalist group believes African Americans constitute an elite class with sovereign immunity placing them beyond federal and state authority.

Sedgwick County Commissioner Sarah Lopez said in an email Tuesday that they are working with law enforcement to find out what the county may be doing to draw the attention of the group.

The FBI said it has been in contact with the local sheriff’s office, but declined Tuesday to provide any additional details about the ongoing investigation.

Meanwhile, the head minister in Wichita of the Moorish Temple of America distanced his religious organization from what he termed the “foolishness” of the Moorish nationalists. Sebastian McGee-Bey said his group is not antigovernment and instead teaches its followers to abide by the law.

“We have been here for about 30 years and we never had any contact with them,” he said. “I didn’t know they were in this area anyway.”