WASHINGTON — A key House committee has subpoenaed the owner of 8chan, an online message board favored by violent white nationalists including the man suspected of killing 22 people in a mass shooting in El Paso, Texas.

Homeland Security Committee Chairman Bennie Thompson and the panel’s top Republican announced the subpoena Wednesday, saying that “at least three acts of deadly white supremacist extremist violence have been linked to 8chan in the last six months.”