Sydney Sweeney could face criminal charges after hanging bras on the Hollywood sign

In a video shared on Instagram, they then hung lines of bras over the famous letters, and posed in front of the sign afterwards, before removing the lingerie - although it's alleged some were left on the hillside.

Although they reported had a filming permit, they could still be in legal trouble over their actions.

The Hollywood Chamber of Commerce - who own the IP rights to the Hollywood sign's image - have revealed a "license or permission" is needed to access the landmark, which is managed by the Hollywood Sign Trust.

The chamber's president and CEO Steve Nissen told ABC News in a statement: "The production involving Sydney Sweeney and the Hollywood Sign was not authorised by the Hollywood Chamber of Commerce nor did we have prior knowledge of it.

"The Hollywood Chamber of Commerce owns the intellectual property rights to the image of the Hollywood Sign, so that anyone intending to use and/or access the Hollywood Sign for commercial purposes must obtain a license or permission from the Hollywood Chamber to do so.

"The Hollywood Chamber of Commerce did not grant a license or permission of any kind to the production involving Sydney Sweeney as reported by TMZ, nor did anyone seek a license or permission from the Chamber for that production."

According to TMZ, the team had permission from FilmLA to shoot on location, but it's claimed they didn't have approval to climb, touch or physically alter the sign.

Although the sign is on public land, it's in a restricted area, and there are laws against climbing the structure.

Trespassing on the site itself can lead to a misdemeanour charge, which can result in a fine of up to $1,000, or up to six months in prison.

The Chamber are yet to file a report for trespassing and/or vandalism, and they are still investigating the stunt.

Nissen added: "We are still investigating how and under what authority (if any) the production accessed the site."

TMZ reported that the Chamber also sent a letter to the production company.

It reads: "It has come to our attention that you and crew filmed the Hollywood Sign last night for a production connected with Persuasion Pictures.

"Please be advised that the Hollywood Chamber of Commerce owns the intellectual property rights to use of the image of the Hollywood Sign and neither you nor the production company have sought or received permission to use the images captured for any commercial use."