All four suspected members of the motorbike-mounted crew have been arrested, but the missing jewels, valued at around €88 million, have not yet been recovered.

Thieves who stole more than €88 million in crown jewels from Paris' Louvre Museum in October escaped with barely 30 seconds to spare, a French Senate inquiry said on Wednesday, as lawmakers detailed a cascade of security failures that allowed the gang to slip away in broad daylight.

The parliamentary probe, ordered after the embarrassing 19 October daylight heist, found that only one of two cameras covering the break-in point was functioning and that security staff lacked enough screens to monitor footage in real time.

When the alarm finally sounded, police were initially dispatched to the wrong location, investigators told senators.

"Give or take 30 seconds, guards or police could have intercepted them," Noël Corbin, head of the inquiry, told the Senate's culture committee.

It said the balcony used by the thieves had been identified years earlier as a weak point but never reinforced.

The findings increase pressure on Louvre director Laurence des Cars, who is due to be questioned by lawmakers next week.

All four suspected members of the motorbike-mounted crew have been arrested, but the missing jewels, valued at around €88 million, have not yet been recovered.