Finner made the comments during a Wednesday briefing four days after the initial claim that the guard lost consciousness after he was stuck in the neck.
SEE MORE: 'Concert from hell': Astroworld Fest attendees describe chaos
Eight people died and hundreds were injured at the event, and at least two people Wednesday remained in critical condition at hospitals.
The security guard at the center of the sticking claim was mentioned by Finner during an earlier briefing on Saturday. Finner said the worker was trying to grab or restrain someone during the melee when he felt a prick on his neck before he lost consciousness.
"We did locate that security guard. His story is not consistent with that. He says he was struck in the head," Finner said Wednesday. "He went unconscious. He woke up in the security tent. He says that no one injected drugs in him."
The new information comes as Finner defended his department's response to preparations for the event, as well as the disaster that unfolded.
RELATED: Houston releases permits issued in advance of Astroworld Festival
RELATED: Harris County Judge Lina Hidalgo wants independent investigation into Astroworld Festival tragedy
RELATED: Houston mayor says stopping Astroworld Fest would have made things worse