The provincial Department of Construction said it had submitted comments to its counterpart in Ho Chi Minh City on route options for the proposed extension.
Under the current plan, the roughly 40-km metro line will run from Vung Tau to Phu My, with a long-term orientation to connect with Long Thanh airport.
Two extension options are under consideration. The first would continue from Phu My into Dong Nai and connect directly to the airport. The second would also enter Dong Nai before turning along the Ben Luc-Long Thanh Expressway corridor towards southern HCM City.
Dong Nai said the airport option would better support Long Thanh's operations by providing a rail link from the former Ba Ria-Vung Tau area while improving connectivity between the province's key urban centres and coastal and port areas.
The department also asked Ho Chi Minh City to provide route details as soon as possible to support Dong Nai's integrated urban planning.