YouTube has been forced to issue an apology after its algorithms were yet again caught showing disturbing content to children.

The website's child-focused app – YouTube Kids – was designed to safeguard minors from the more mature offerings found on the main website. But alarming material featuring popular cartoon characters had slipped through the cracks, the BBC said on Tuesday (6 February).

Videos being offered up to young eyes automatically by the site's back-end algorithms showed Mickey Mouse characters with guns and popular children's characters being injured, the BBC found.

According to Newsround, its 'news for children' programme, material included Paw Patrol characters on a burning plane and clowns covered in blood.

Katie O'Donovan, public policy manager at Google, which owns YouTube, told the BBC she was "very sorry for any hurt or discomfort" caused by the content.

YouTube said it was investing in machine-learning technology to "identify the most harmful content" and have it removed before being published.

"It is a difficult environment because things are moving so quickly," a spokesperson added.

The news came two months after a series of scandals revealed that "child exploitation" videos were being uploaded to the service. Some showed children in revealing clothing being forced to take part in "gross out" scenarios and kidnapping roleplays.

The main YouTube website, which boasts more than one billion users worldwide, pledged swift action to purge the content, some of which had racked up tens of millions of views. Officials said they had removed thousands of videos under a set of newly updated guidelines.

"In the last couple of weeks we expanded our enforcement guidelines around removing content featuring minors that may be endangering a child, even if that was not the uploader's intent," said Johanna Wright, YouTube's vice-president of product management.

"We will continue to work quickly to remove more every day," she continued. "We're wholly committed to addressing these issues and will continue to invest the engineering and human resources needed to get it right. As a parent I'm determined that we do."

But the same month, it emerged that its algorithms used for autocomplete results had been hijacked to show "profoundly disturbing" results, such as "how to have s*x with your kids".

A video showing adults dressed as clowns restricting a child with tape notched up 3,867,883 views Screenshot/YouTube