TOPEKA, Kan. (AP) — The Kansas secretary of state’s office received a letter Tuesday containing what Secretary Scott Schwab called “a suspicious substance.” Officials evacuated the building for the rest of the day.

Schwab’s office serves as the state’s top elections authority, and the incident occurred less than a week after election offices in at least five states states received threatening mail. Some of that mail contained the potentially dangerous opioid fentanyl.

The Kansas Bureau of Investigation, taking the lead in the case, did not provide further details about the letter received Tuesday, and Schwab did not say what the suspicious substance was.

“With recent events, we take such things as a suspicious substance very serious,” Schwab said in a text to The Associated Press. “Our team is trained if they see something, say something.”

The KBI is working with the Kansas Highway Patrol, the state fire marshal’s office and the state Department of Health and Environment, spokesperson Melissa Underwood said in an emailed statement. She said authorities evacuated the building, which also houses the Kansas attorney general’s office, “out of an abundance of caution.” The building that was evacuated is located near the Statehouse.

“The investigation is ongoing,” Underwood said, adding that Kansas has experienced only one such incident so far.

An officer inside the building Tuesday afternoon said it still was being secured. Two people who worked there went to the main entrance to have officers retrieve items left behind. They declined to comment afterward.

Local television station WIBW reported that its crews saw Topeka Fire Department hazardous materials teams entering the building shortly after it was evacuated. They were gone by the afternoon.

In June, dozens of Republican officials in Kansas, Montana and Tennessee received threatening letters containing white powder, though tests did not detect toxins and no injuries were reported. Authorities have yet to announce arrests.

Schwab is a Republican who has pushed back against baseless theories about the 2020 election being stolen. The motivation of anyone responsible for suspicious mail delivered in other states last week was unclear.