NEW YORK • Facebook and other social networks are under scrutiny following the Orlando massacre and the murder of a French policeman and his partner this week.
Facebook has said it was cooperating with the French authorities probing the murders, which included a live-streamed video statement on the leading social network.
In Washington, a top US lawmaker said the authorities were probing the Facebook activity of the Orlando nightclub shooter after an investigation found Omar Mateen made extremist posts during the massacre and searched for news of his attack.
"We are working closely with the French authorities as they deal with this terrible crime," Facebook said in a statement on Tuesday following Monday's fatal stabbing of 42-year-old police commander Jean-Baptiste Salvaing and his 36-year-old partner, Ms Jessica Schneider, in a town near Paris.
"Terrorists and acts of terrorism have no place on Facebook. Whenever terrorist content is reported to us, we remove it as quickly as possible. We treat takedown requests by law enforcement with the highest urgency."
After the stabbings but before he was killed in a police raid, 25-year- old Larossi Abballa - a known radical claiming allegiance to the Islamic State in Iraq and Syria (ISIS) terrorist group - issued threats in a video statement posted on Facebook Live, a new feature that enables any user to stream a live event.
The incident posed a new challenge for Facebook and other social networks seeking to keep an open platform without allowing users to promote violence.
"We do understand and recognise that there are unique challenges when it comes to content and safety for Live videos," a Facebook spokesman said. "It's a serious responsibility, and we work hard to strike the right balance between enabling expression while providing a safe and respectful experience. We are deeply committed to improving the effectiveness of how we handle reports of live content that violates our community standards."
Facebook, which has more than 1.5 billion members worldwide, last year updated its so-called "community standards" to make clear it does not want the platform used to incite attacks or violence. Other social networks have made similar efforts, but monitoring and policing the feeds is a difficult task, and the platforms are often unable to prevent sensitive content from being posted.
In Washington, Mr Ron Johnson, the Republican chairman of the Senate Committee on Homeland Security, sent a letter to Facebook chief Mark Zuckerberg on Wednesday asking the company to share specifics of five accounts apparently used by Omar.
Lawmakers are trying to determine if there are ways for intelligence and law enforcement communities to monitor social media platforms like Facebook "so that we can prevent these tragedies", Mr Johnson told CNN on Thursday.
"This is our job, to see what has happened in the past, what can we possibly do to prevent this from occurring in the future and how can we find bipartisan solutions," the Republican said.
Omar killed 49 people and wounded 53 in his shooting spree early on Sunday at the Pulse gay nightclub in the Florida resort city of Orlando.
In his letter to Mr Zuckerberg, Mr Johnson said Omar apparently posted some time during the attack that he was pledging allegiance to ISIS' leader, and "America and Russia stop bombing the Islamic state".
He also allegedly posted "The real Muslims will never accept the filthy ways of the West" and "In the next few days, you will see attacks from the Islamic State in the USA".
Omar also allegedly searched for "Pulse Orlando" and "shooting", Mr Johnson said.