NEW DELHI — An Indian appeals court on Monday acquitted 35 crewmembers and security guards of a private U.S. ship, including six former British soldiers and 10 Indians, who were sentenced last year to five years in prison on charges of illegally transporting weapons and ammunition in Indian waters in 2013.

Justice M. Basheer Ahamed said the charges against them had not been proven. He also said a fine of 3,000 rupees ($65) paid by each would be returned, the Press Trust of India news agency reported.

The Herndon, Virginia-based company that owned the ship said the vessel was involved in anti-piracy operations and had not strayed into Indian waters.

Police seized 35 automatic weapons and about 5,700 rounds of ammunition from security guards on the ship.

Prosecutors told the court in the southern city of Madurai that the crewmembers and security guards, who also included Estonians and Ukrainians, on the MV Seaman Guard Ohio were arrested after they failed to produce documents allowing them to carry the weapons.

The ship is owned by the security company AdvanFort, but is registered in Sierra Leone. It was detained in October 2013 and has been in Tuticorin port in southern Tamil Nadu state.

The ship’s captain told investigators that the company provided armed escorts for merchant vessels traveling in pirate-inhabited waters in the Indian Ocean.

India is very sensitive about the presence of armed security guards on merchant ships after Italian marines fatally shot two fishermen in 2012. The marines, part of a military security team on a cargo ship, fired at the fishermen, mistaking them for pirates. The two Italians are facing trial in India over the deaths.