Federal and state authorities are investigating suspicious mail containing a white powder that was received by a north Louisiana church attended by House Speaker Mike Johnson.

Cypress Baptist Church in Benton received the package Monday, Johnson’s Washington office said.

“Speaker Johnson and the Johnson family thank U.S. Capitol Police, the FBI, the Louisiana State Police, and the Bossier Parish Sheriff’s Office for taking swift action and handling the situation professionally,” Johnson spokesman Griffin Neal said in an emailed statement Tuesday.

Authorities have not said who the letter was addressed to or what they believe the white powder to be.

The FBI issued a statement that didn’t mention the church’s name but saying it was investigating a letter containing white power sent to an address on Benton’s Palmetto Road, the road on which the church is located. The FBI statement said a field test on the substance was negative, but more testing was planned, adding that “even sending a hoax letter is a serious crime.” The agency declined to answer questions.

Neal’s statement said the Cypress Baptist is Johnson’s “home church.” KTBS-TV reported that Johnson’s wife, Kelly, who manages a counseling service, has an office at the church.