The company inked two ships at the yard in July and a source close to the organisation confirms two options have now been declared.
All four units are now scheduled for delivery in 2017 and they are understood to be costing $52m each.
Harry Vafias-controlled StealthGas is primarily an owner of small LPG carriers with a fleet of around 40 units.
The company is time charter orientated and has secured more period employment for two of its ships.
Petrobras
