The departure of the master of a Fratelli d’Amico Armatori tanker from Peru during an oil spill investigation has sparked controversy as officials pursue a $4.5bn lawsuit targeting several companies over the January incident.

Peruvian prosecutors have requested the extradition of Captain Giacomo Pisani and chief officer Nitesh Kumar as part of a continuing investigation into a spill that took place when the 158,300-dwt Mare Doricum (built 2009) was unloading a cargo of crude at a Repsol refinery near Lima.