The California state Senate confirmed Wednesday that red liquid inside a menstrual cup hurled at lawmakers from a viewing gallery by an anti-vaccine protester last month was human blood.

“While lab tests confirmed that the substance thrown from the Senate Gallery was human blood, it was negative for any blood borne [sic] pathogens or infections,” Erika Contreras, secretary of the Senate, wrote in a letter to staffers.

Contreras also wrote that an environmental hazard company was hired to "ensure complete remediation and decontamination of both the chamber and the gallery," according to the San Francisco Chronicle, which obtained a copy of the letter.

Rebecca Lee Dalelio, 43, allegedly hurled the blood onto the Senate floor in opposition to Senate bills 276 and 714 on Sept. 13, the final day of the legislative session,

She allegedly yelled: "That's for the dead babies" before throwing the cup at lawmakers. At least six senators were hit by the menstrual cup or the blood. A menstrual cup is a silicone or latex cup that collects menstrual fluids.

Democratic State Sen. Steve Glazer underwent a series of tests after he said he was hit in the head with blood, the Sacramento Bee reported.

“A couple hours of sleep since our Senate adjournment around 3am [sic] and I’m at a doctors [sic] appointment to follow safety protocols from blood exposure,” Glazer tweeted.

Both bills, which give the state the power to review medical exemptions for vaccines, were signed into law earlier that week by Democratic Gov. Gavin Newsom, prompting vaccine skeptics to flood the state Capitol in Sacramento.

Investigators initially called the substance a "feminine hygiene device" containing what appeared to be blood. The Senate chamber was evacuated and the session resumed three hours later in another room.

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Dalelio was arrested without incident on suspicion of six crimes, including assault and vandalism.

“This incident was incited by the violent rhetoric perpetuated by leaders of the anti-vaxx movement,” said Sen. Richard Pan, who wrote both bills to reinforce laws that ban personal beliefs from a list of reasons to obtain vaccine exemptions. “As their rhetoric escalates, their incidents of violence does as well. This is an attack on the democratic process and it must be met with strong condemnation by everyone.”