CCTV footage captured the thieves entering the museum grounds by cutting through a fence before cutting through the structures holding the paintings' frames. The alarm went off at 05:48 local time (03:48 GMT), and police were at the scene within five minutes. The thieves fled upon hearing the alarms, leaving two of the four paintings behind in the gardens.
Mayor Bryan Masson described the thieves as "well-equipped" and "well-informed," noting they were wearing helmets, gloves, and combat gear, and carrying an electric knife and a hacksaw. Investigators have found two zip-up bags at the scene that may belong to the suspects.
The two paintings still missing are Portrait of Madame Colonna Romano (1910) and Jeune fille au puits (1886). The two recovered works have not been named.
The heist is the latest in a string of high-profile art thefts in Europe, including a brazen robbery at the Louvre Museum in Paris last October, where France's priceless crown jewels were stolen.