“We are not yet where we need to be on the issues of suicide and self-harm,” Instagram head Adam Mosseiri wrote in a piece in the Telegraph. “We rely heavily on our community to report this content, and remove it as soon as it’s found. The bottom line is we do not yet find enough of these images before they’re seen by other people.”

The op-ed comes several months after a Telegraph investigation revealed a number of Instagram accounts that incited young people into harming themselves, through images of self-harm and user comments that encouraged people to escalate their self-harming activities. “Users of the popular social media network who like self harm accounts are being ‘recommended’ similar accounts and graphic images to see and follow,” the newspaper reported.

Mosseri wrote that he was “deeply moved” and “horrified” by recent reports of young people and families affected by suicide and self-harm. He mentioned Molly Russell, a British teenager who killed herself after struggling with depression. Russell’s parents have since said she followed multiple self-harm and suicide accounts on Instagram and Pinterest.

But Mosseri only vowed changes to address the issue after Matt Hancock, the U.K.’s health secretary, warned Facebook and other tech giants that he would use the law to force them to protect their young users from harmful content, should the companies prove unwilling or unable to do so themselves.

In the op-ed, Mosseri outlined changes Instagram is making to address self-harm and suicide content, including training workers to spot such images, applying “sensitivity screens” that will make self-harm images less accessible, and supporting people whose posts indicate they may be struggling with self-harm or suicide.

Mosseri, who had previously overseen Facebook’s news feed, was named head of Instagram last October after the app’s co-founders—ex-CEO Kevin Systrom and ex-CTO Mike Krieger—abruptly left Facebook amid a disagreement over Instagram’s strategy.

Facebook, which bought Instagram for $1 billion in 2012, saw its stock rise $3.54 a share, or 2.1%, to $169.25 a share Monday.