They say the loot worth some €4.5m (£4m; $5.4m) was in a bag dropped by one member of the five-strong gang during the brazen raid.
Three men have been arrested, police said, while others remain on the run.
The five-star Ritz is in Place Vendôme, in Paris' historical first district on the right bank of the river Seine.
"I can confirm that all the stolen jewels were found in the bag recovered by police officers," a source close to the investigation was quoted as saying by Reuters.
The gang used axes to smash the shop's windows on the ground floor of the hotel at about 18:00 local time (17:00 GMT).
Le Parisien newspaper, citing a police source, reported that the robbery was interrupted by an officer on patrol.
Three robbers were later arrested after being blocked in the building.
But another two thieves, who waited outside, managed to escape by car and scooter.
The stolen jewels were found in the bag dropped by the thief on the scooter, the sources say, as he collided with a pedestrian.
Meanwhile, the getaway car used by his accomplice was later found in Sannois, just north of the French capital.
The luxurious hotel is located next door to the French justice ministry.