A red liquid that was thrown by an anti-vaccine activist onto the floor of the California State Senate earlier this month has been determined to be human blood, according to chamber officials.

In a letter to staffers on Wednesday, Secretary of the Senate Erika Contreras wrote that “lab tests confirmed that the substance thrown from the Senate gallery was human blood” but that it was “negative for any blood borne pathogens or infections.”

The Senate took several security measures to ensure the chamber was decontaminated after the “unanticipated attack,” hiring a state-certified health hazard assessment company to clean up the mess, the letter read.

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California Highway Patrol officers arrested 43-year-old Rebecca Dalelio on assault and vandalism charges after she allegedly dumped what officials then deemed red liquid that “appeared to be blood” from a menstrual cup on lawmakers from the chamber’s gallery on Sept. 13, the Los Angeles Times reports.

Multiple lawmakers appeared to be hit by the liquid. One official, state Sen. Steve Glazer (D), tweeted Sept. 14 that he went to the doctor after the incident.

Dalelio and a group of anti-vaccine protesters had stormed the state Capitol on the last day of the chamber’s session to voice opposition to bills signed by Gov. Gavin Newsom Gavin NewsomOVERNIGHT ENERGY: California seeks to sell only electric cars by 2035 | EPA threatens to close New York City office after Trump threats to 'anarchist' cities | House energy package sparks criticism from left and right California seeks to sell only electric cars by 2035 EPA head questions connection of climate change to natural disasters MORE (D) that allowed the review of medical vaccine exemptions for children attending school.

“That’s for the dead babies,” one protester shouted as the blood was dumped on the lawmakers.

Lawmakers were immediately forced to leave the chamber and security cleared the gallery as authorities responded to the incident.