According to AdvanFort there were privately contracted security personnel on board the Sierra-Leone registered MV Seaman Guard Ohio.
It said that as these men routinely provide counter-piracy protection they also had uniforms, protective equipment, medical kits, rifles and ammunition - "all of which is properly registered and licensed to AdvanFort".
The company added that the vessel "provides an accommodations platform for AdvanFort's counter-piracy guards between transits on client commercial vessels transiting the high risk area".
Analysts say that anti-piracy measures on high-risk shipping routes are poorly regulated and India is increasingly sensitive to violations of its maritime boundaries.
India directly supports the multi-national campaign to combat the mostly Somali pirates targeting ships in the Indian Ocean with its own navy.
But it's been controversial too, with the Indian authorities prosecuting two Italian marines on anti-piracy duty for allegedly shooting two fishermen inside Indian waters last year.
They were guarding an Italian oil tanker and said they mistook the fishermen for pirates.