Hartford, Connecticut: YouTube will remove videos claiming the Sandy Hook shooting didn't happen as it updates its hate speech policy, the company said.

"We will begin enforcing this updated policy today; however, it will take time for our systems to fully ramp up and we'll be gradually expanding coverage over the next several months," the Google-owned video site said on Wednesday.

A US flag flies at half-mast on Main St in honour of the 26 students and staff killed in a mass shooting at the Sandy Hook Elementary school in Newtown, Connecticut in 2012. Credit:AP

The families of the 20 children and six educators killed in the December 14, 2012 shooting in Newtown have spent years fighting conspiracy theorists on the internet, including those who claim the shooting was a hoax carried out to win support for stricter gun laws.

Internet radio host Alex Jones is facing numerous defamation lawsuits filed by the Sandy Hook families for stating on his InfoWars program that the victims' families were actors. The families say they have faced death threats and online abuse as a result.