When was the new Enfield Rifle with greased cartridges introduced in the British Indian Army?

Explanation

In December, 1856, the government decided to replace the old Brown Bess musket with the new Enfield rifle. Training for these rifles was to be given at Dum Dum, Ambala and Sialkot. These rifles used greased cartridges, which were said to be coated with the fat of cows and pigs. In this rifle, the upper part of the cartridge had to be bitten off with the mouth. In January, 1857, a rumour spread in the Bengal Army that the greased cartridges contained the fat of cows and pigs. The military officers denied it immediately without proper investigation. But the soldiers became convinced that the use of such cartridges was a deliberate attempt to corrupt their religion, and this became the immediate cause of the Revolt of 1857.