Just hours before the opening ceremony, there was chaos on the rail network in and around Paris after a series of acts of deliberate sabotage. Signal boxes and fibre-optic cables on the high-speed rail system were vandalized, causing fires and affecting around 800,000 people, including on Eurostar, for however long. We just want to get out to Paris, so that's the thing.In France, engineers are still racing to fix the damage, replacing cables on three affected lines, including this one, heading due west from Paris to the Atlantic Coast. It's already easing the strain in the French capital.There are plenty There are frustrated travelers here, but the good news is that while the high-speed lines have been affected across France, the bulk of the rail network is still operating just fine and is trying to pick up the slack.Progress then, but this has been an alarming experience for a city anxiously hoping nothing else will go wrong this Olympic summer.So tonight, Rita, a huge manhunt underway across France. Investigators searching at least four crime scene sites for forensic evidence. The interior minister here saying he's hoping for swift arrests, but still no suspects found, no claims of responsibility, and although there's a lot of finger-pointing, no clear idea yet which group or even foreign nation may be behind this. Of course, the lingering concern that this may not have been a one-off attack and that France will have to be on guard still for these weeks ahead.Thank you very much. Andrew Harding reporting there. Well, I'm joined by our security correspondence, Gordon Carrera. Who could be behind these attacks, Gordon?Well, it's not clear yet. I think what's noticeable about these attacks, though, is just how well-planned they were. You had all this intense security in Paris, tens of thousands of police and troops. Yet these individuals were able to go outside of Paris to the middle of nowhere and carry out a coordinated attack to know exactly where to go to hit those cable junction points at the most damaging place. That suggests a lot of reconnaissance, perhaps inside knowledge. Their aim also looks to have been to disrupt as much as possible, not to injure or to kill. That points you away from the jihadist terrorist motive, which is one of the threats France has been worried about for these games. But there are other threats. There's the Russians, angry at France over Ukraine, also not able to compete under their own flag at the Olympics. There was an arrest just in the last week of an individual, a Russian in France, a 40-year-old, posing as a chef who was alleged to have been linked to Russian intelligence, planning to disrupt the games, but also domestic threats and groups that France has been worried about. Anarchist groups, far-left groups who don't like the Olympics, don't like the French government.I think the fact they've carried out some similar attacks in the past led some officials to suggest in the early moments this morning that they might be the most likely culprits, but no confirmation yet. I think security officials will have been really concentrating on that opening ceremony, and there will be a lot of relief that that appears to have gone without any major security incidents despite the travel disruption.

for however long. We just want to get out to Paris, so that's the thing.

In France, engineers are still racing to fix the damage, replacing cables on three affected lines, including this one, heading due west from Paris to the Atlantic Coast. It's already easing the strain in the French capital.

There are plenty There are frustrated travelers here, but the good news is that while the high-speed lines have been affected across France, the bulk of the rail network is still operating just fine and is trying to pick up the slack.

Progress then, but this has been an alarming experience for a city anxiously hoping nothing else will go wrong this Olympic summer.

So tonight, Rita, a huge manhunt underway across France. Investigators searching at least four crime scene sites for forensic evidence. The interior minister here saying he's hoping for swift arrests, but still no suspects found, no claims of responsibility, and although there's a lot of finger-pointing, no clear idea yet which group or even foreign nation may be behind this. Of course, the lingering concern that this may not have been a one-off attack and that France will have to be on guard still for these weeks ahead.

Thank you very much. Andrew Harding reporting there. Well, I'm joined by our security correspondence, Gordon Carrera. Who could be behind these attacks, Gordon?

Well, it's not clear yet. I think what's noticeable about these attacks, though, is just how well-planned they were. You had all this intense security in Paris, tens of thousands of police and troops. Yet these individuals were able to go outside of Paris to the middle of nowhere and carry out a coordinated attack to know exactly where to go to hit those cable junction points at the most damaging place. That suggests a lot of reconnaissance, perhaps inside knowledge. Their aim also looks to have been to disrupt as much as possible, not to injure or to kill. That points you away from the jihadist terrorist motive, which is one of the threats France has been worried about for these games. But there are other threats. There's the Russians, angry at France over Ukraine, also not able to compete under their own flag at the Olympics. There was an arrest just in the last week of an individual, a Russian in France, a 40-year-old, posing as a chef who was alleged to have been linked to Russian intelligence, planning to disrupt the games, but also domestic threats and groups that France has been worried about. Anarchist groups, far-left groups who don't like the Olympics, don't like the French government.

I think the fact they've carried out some similar attacks in the past led some officials to suggest in the early moments this morning that they might be the most likely culprits, but no confirmation yet. I think security officials will have been really concentrating on that opening ceremony, and there will be a lot of relief that that appears to have gone without any major security incidents despite the travel disruption.