A Maine initiative intended to limit transgender students' ability to participate in sports has been removed from the ballot because of invalid signatures, the secretary of state ruled Tuesday.

The proposal from parents' group Protect Girls Sports in Maine was slated to go before voters in November. It would have asked voters if they wanted to require public schools to restrict access to bathrooms and sports based on the gender denoted on a child's birth certificate.

Maine Secretary of State Shenna Bellows, who is running for governor as a Democrat, said Tuesday her staff found that more than 12,000 signatures on the petition for the referendum were invalid. That leaves the petition drive a few hundred short of the 67,682 required for the initiative to make the ballot, Bellows said.