Similar to most Polish senators, Grodzki is in opposition to the ruling Law and Justice party.
"This is the product of the industry of contempt and incitement toward political opponents. A package came to the Senate in my name [containing] a letter with death threats and explosive substance," Grodzki said on Twitter.
"The parcel was retreated by the relevant services. I hope they will manage to seize the perpetrator promptly," he added.
The investigation into the incident is underway.