Flight AF 463, headed from Mauritius to Paris, which had 459 passengers and 14 crew members on board, had left Mauritius at 9.00 pm (10.20 pm IST) and had been due to arrive in Paris Charles de Gaulle at 5.50 am (10.20 am IST).
But it made an emergency landing at Moi International Airport in the southern port city of Mombasa at 12.37 am local time.
"It requested an emergency landing after a device suspected to be a bomb was discovered in the lavatory, an emergency was prepared and it landed safely and all passengers evacuated," police spokesman Charles Owino said.
"Bomb experts from the navy and the CID were called in and took the device which they are dismantling to establish if it had any explosives," he said.
The plane was still at Mombasa airport in the morning, he added.
"We still do not know what type of object it was," an Air France spokesman later said.
"The Kenyan authorities are continuing their investigation and we remain in contact with them."
He said the airline planned to fly the passengers to Paris from Mombasa on another flight later on Sunday.
While the airline "regrets the inconvenience and the delay that was caused to its customers," its "priority is to ensure the safety of its passengers," he said.
Picture for representation only.