FILE PHOTO: Homeland Security Committee Chairman Bennie Thompson (D-MS) listens to testimony from Department of Homeland Security Secretary Kirstjen Nielsen during a House Homeland Security Committee hearing on “The Way Forward on Border Security” on Capitol Hill in Washington, U.S., March 6, 2019. REUTERS/Joshua Roberts

WASHINGTON (Reuters) - The U.S. House Homeland Security Committee said Wednesday it had subpoenaed online message board 8chan owner Jim Watkins to testify on Sept. 5 as part of its probe into countering extremist content on social media platforms.

Last week, the panel had demanded Watkins, an American living in the Philippines, testify. Representative Bennie Thompson, a Democrat and the panel’s chairman, and Mike Rogers, its ranking Republican, said the shooting deaths of 22 people at an El Paso Walmart store was “at least the third act of supremacist violence linked to your website this year.”

The pair said, “receiving testimony from Mr. Watkins is critical to our oversight on this matter.”