They have however stated it was an explosive device, the explosives expert also gave an assessment as follows:
“An Explosives and Hazardous Devices Examiner with the Federal Bureau of Investigations was unable to conclusively identify the precise dimensions, charge size, or whether the device thrown was improvised or commercially manufactured; however, based on reviewing the various video angles that captured the explosive was able to conclude the device was capable of inflicting damage to surrounding property as well as seriously injuring persons in the vicinity of the resultant explosion. Several officers were injured as a result of the explosion.”
https://www.justice.gov/usao-dc/pr/florida-man-arrested-felony-charges-actions-during-jan-6-capitol-breach-0