Two Zondervan employees in Cascade Township, Mich., became ill Monday after opening a suspicious package in the mailroom.

According to WOOD TV8, the workers experienced upper respiratory problems, including coughing and difficulty breathing. Zondervan President Doug Lockhart said that a powdery material had leaked from the package.

One employee, Carolyn Weidmayer, was rushed to a hospital, while the other sick worker was treated on-site. Weidmayer was discharged from the hospital in stable condition less than three hours after being admitted, the Grand Rapids TV station reported.

Other Zondervan employees were sent across the street to the Krispy Kreme headquarters for possible treatment, WOOD TV8 reported.

Zondervan spokesperson Vicki Cessna said emergency workers removed the suspicious package from the scene for testing and analysis. No hazardous materials were found inside the package, Cessna added.

Cessna told Christianity Today that employees were allowed to return home for the day. The employees returned Tuesday, and the Zondervan office was open for regular business hours.