Madrid's regional government is assessing how to get a bus campaigning against allowing children to change their gender off the Spanish capital's streets.
The orange-and-white bus has several phrases written on its sides, including: "If you're born a man, you're a man. If you're a woman, you will always be a woman."
The bus appeared on Monday and is the brainchild of the Hazte Oir (Make Yourself Heard) organisation, which has previously campaigned against abortion.
It came in response to a campaign last month by an association of families of transgender children that aimed to raise awareness of the issue.
The regional government said it is consulting with police over whether the bus breaks anti-discrimination laws.
The bus is due to visit seven other Spanish cities in coming days.