WICHITA, Kan. (AP) – 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 two employees and forcing several more to undergo decontamination.

The Sedgwick County Finance Department in the county courthouse received the certified letter on Monday, the Wichita Eagle reported.

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 said. One of the employees was sent to a hospital for observation. Both are expected to be OK.

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 Sedgwick County Sheriff’s Office said in a news release.

Stolz said the letter purported to come from Moorish nationalists, but the origin of the letter remains under investigation.

The Southern Poverty Law Center defines Moorish nationalists as people who believe African Americans constitute an elite class with sovereign immunity that places them beyond federal and state authority.