A gallery attendant on duty at the Louvre when thieves broke in and stole eight of France's crown jewels has said no-one could have been prepared for what unfolded as visitors began to arrive on Sunday morning.

All of a sudden we heard a huge noise, she told radio station France Inter, in the first account given by an attendant at the scene.

The unnamed attendant and two colleagues initially thought the noise to be an angry visitor, but it was not a normal sound: It was a dull, slightly metallic noise. It was, in fact, the moment thieves had used an angle grinder to burst through a reinforced window into the Gallery of Apollo, where the Louvre's collection of historic jewelry is kept.

Within eight minutes, the gang seized treasures, including a necklace that belonged to Napoleon's wife Empress Marie-Louise and a diadem of Napoleon III's wife Empress Eugenie, worth an estimated total of €88m (£77m). The thieves used a mechanical ladder on the back of a lorry to lift themselves to a first-floor balcony to gain entry to the gallery.

Two tourists ran towards them in panic, she said. I saw one of the criminals turn around with something that looked to me like a chainsaw, then I yelled at my colleagues to get out, she recalled. She shouted a second time that it was a robbery and that they should run.

One of her colleagues raised the alarm over a walkie-talkie and then we finished evacuating the visits without quite realizing what was going on. They shut all the doors as they left to protect the neighboring galleries.

On reflection, the attendant said for us it was unbelievable the display cases could have been broken... never for a moment did we think there was such a risk... nobody can be prepared for that.

Another Louvre employee came forward to describe the moments after the gang escaped. The anonymous security guard spoke of a very strong smell of petrol as he arrived at the scene outside the Louvre where the gang had parked their lorry.

I ran outside through the [glass] pyramid and across the courtyard... I got there at the very moment the criminals got away by scooter, he told BFMTV. The gang had ruptured the lorry's fuel tank and there was a blowtorch nearby, he said. It's clear they intended to set fire to their vehicle. I genuinely think we thwarted their plan because they would never have left behind so much evidence.

During the panic, they even lost one of the pieces they'd meant to steal, as Empress Eugenie's crown fell onto the ground during their hasty escape. Although the crown was found, it was damaged.

The museum's director, Laurence des Cars, commented on security challenges, noting that the empress's crown might undergo delicate restoration. Despite their insistence on the security measures, the situation raised concerns about the declining culture of security at the museum.