French investigators have taken four additional suspects into custody as the probe into last month’s dramatic theft of imperial jewels from the Louvre deepens, Paris prosecutor Laure Beccuau said on Tuesday.

The suspects, two men aged 38 and 39 and two women aged 31 and 40, are all from the Paris region. Their arrests follow earlier charges brought against four others linked to the October 19 heist.

The theft, carried out by a four-person gang, unfolded in broad daylight and lasted only seven minutes. The group parked a moving truck below the Louvre’s Apollo Gallery, used a ladder and bucket to reach a window, then smashed their way inside. They cut through glass display cases containing French crown jewels with angle grinders and fled on scooters with jewelry valued at about $102 million.

Four people have already been charged, including three men and one woman. Beccuau previously said one of the men, a 37-year-old, was in a relationship with the woman and they have children together.

During their escape, the thieves dropped a diamond and emerald crown that once belonged to Empress Eugenie, the wife of Napoleon III. They managed to get away with eight other pieces, among them an emerald and diamond necklace Napoleon I gave to Empress Marie-Louise.

The stolen items remain missing.