After Islamic State claimed responsibility for the Champs Elysée shooting, and identified the attacker as "Abu Yousif the Belgian", some media outlets reported a Belgian connection involving a supposedly unsafe individual called Osri who was en route to France on the Thalys.
The officials spoke on condition of anonymity because they weren't authorised to publicly discuss details of the probe into Thursday night's attack.
The attacker was identified from papers left in his vehicle.
National police spokesman Jerome Bonet said there were thousands of people on Paris' famous boulevard when the gunman opened fire and the rapid response of officers who shot and killed him avoided possible "carnage".
Cheurfi, 39, a French national who lived with his mother in the eastern Paris suburb of Chelles, had spent some 14 years in prison from 2001 for crimes including gun attacks on law enforcement officers.
The gunman was shot dead by police in the van while he was trying to flee the scene on foot.More news: Gonzalez, Nationals beat Mets 3-1 for 6th straight win
Thousands of troops and armed police have been deployed to guard tourist attractions such as the Champs-Elysees or other potential targets like government buildings and religious sites.
Members of the same cell then carried out the March 22 bombings in Brussels past year that killed 32 people and wounded hundreds more.
Two French officials said the gunman was detained towards the end of February after speaking threateningly about the police, but he was then released due to a lack of evidence.
Early yesterday, the authorities were looking for a second suspect in connection with the incident.
US President Donald Trump on Friday said the Paris attack "will have a big effect" on France's presidential vote.
"Over the next few days more than 50,000 police officers and gendarmes will be mobilised to ensure a calm and peaceful election". Investigators suspect they had planned another attack in Paris before police had closed in on them.More news: Napa County unemployment rate drops
Francois Fillon, who is the conservative candidate, said he would cancel the campaign events had had been planning for Friday as a result of Thursday's attack.
So close to the presidential election, "the country's on edge", Eleanor says, adding that thousands of police officers are on the streets.
In a statement from its Amaq news agency, the group gave a pseudonym for the shooter, Abu Yusuf al-Beljiki, indicating he was Belgian.
One police officer killed, two others were injured and a female tourist was also hurt before police shot and killed the suspect.
He used a Kalashnikov assault rifle to shoot the officer twice in the head, Paris prosecutor Francois Molins said.More news: Aaron Hernandez's Family Schedules Monday Funeral In Connecticut
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