What caused the Brazilian сruiser, Bahia to sink?

Bahia was the lead ship of a two-vessel class of cruisers built for Brazil by the British company Armstrong Whitworth. It was commissioned in 1910 and was sunk by an explosion on July 4th, 1945.

On 4 July 1945, she was stationed northeast of Brazil around 0°N 30°W, near Saint Peter and Saint Paul Archipelago, in a mission of patrolling in the Atlantic. For anti-aircraft target practice, crewmen were firing the ship's 20 mm guns at a kite that was being towed behind the ship. One of them shot it down, but also accidentally hit the depth charges on the stern—a direct consequence of the lack of guide rails that would normally prohibit the guns from being aimed at the ship.The resulting explosion knocked out all power on the ship and sank her in about three minutes.

The survivors of the blast endured four or five days of no food, high temperatures and full exposure to the sun on their makeshift rafts. Some were driven mad by these conditions and simply jumped into the water, where they were devoured by sharks. The official history of the ship gives 36 rescued and 336 dead, and the Navios de Guerra Brasileiros gives 36 and 339.

Rescued crewmen believed that they had hit a mine that detonated one of the ship's magazines. Some officials claimed that Bahia could have been mined or torpedoed by German submarines. However, military investigations concluded that the cruiser had been indeed sunk due to the above-described gunnery accident.