France is still facing travel disruption a day after saboteurs targeted high-speed railway lines in an attack coinciding with the start of the Olympics. As operators try to get service back to normal, a key question remains – who was responsible?

Authorities are investigating what outgoing French Prime Minister Gabriel Attal called a “coordinated” effort. He said that intelligence services and internal security forces are involved in inquiries and urged caution over jumping to conclusions.

No-one has yet claimed responsibility for the attacks, but given their scale, timing and precision, it is clear they are more than just random acts of vandalism.

There are many possible culprits – the opening day of the Olympic Games is one of the most watched events in the world, a tempting target for anyone seeking to cause chaos and disruption in the limelight.

Here’s what we know.

Extensive knowledge of railways

High-speed trains connecting southwestern, northern and eastern regions of French were all impacted on Friday, in what authorities described as a methodical pattern of attacks hitting key arterial routes.

The perpetrators have extensive knowledge of the network, according to Axel Persson, a leader of the CGT rail union. They must have had access to very “precise information,” he added.

Employees had implemented a failsafe plan in preparation for the Olympics, allowing some passengers to use alternative lines that would slow down traffic, but at least travelers would get to their destination, Persson added. “France is disrupted but not paralyzed,” he said.

Jean-Pierre Farandou, the CEO of state-owned rail company SNCF, told journalists that cables – which are there to ensure the security of train drivers – were set on fire and taken apart but again stressed authorities “don’t know who is behind it.”

An act of protest?

France is no stranger to widespread strikes or political demonstrations that manifest into blocked transport links across the country.

The parliamentary election held just weeks ago attracted large scale protests and rallies. However, such events tend to be announced in advance and those behind them are keen to make their cause known.

Environmental activists have previously blocked traffic to bring attention to the climate crisis. But these groups have mostly staged bold and striking demonstrations focused on fossil-fuel intensive transportation, such as on airports and highways, and also make it known when they are behind such protests.

The last major act of vandalism on high-speed train lines in France was in 2008, when steel rods were placed on overhead power cables. Police arrested individuals from an alleged anarchist group from Tarnac village but 10 years later, after a lengthy investigation, they were all acquitted and cleared of sabotage.

Foreign actors?

Recently, France has been one of several countries impacted by a wave of suspected Russian sabotage attacks against infrastructure and other targets.

French President Emmanuel Macron has remained a staunch ally of Kyiv throughout the fighting. Just in May, he suggested that Ukraine should be allowed to use their weapons against targets inside Russia from which the Kremlin attacks Ukraine.

Earlier this week, French authorities detained a Russian citizen in Paris, accusing him of preparing destabilizing events during the Games. Kremlin spokesperson Dmitry Peskov said Russia did not have any information on the arrest.