Mwangura said the United Arab Emirates-owned vessel was on route to Durban (South Africa) from Mombasa (Kenya) when it was attacked by the gun wielding pirates.
"The MT Asphalt Venture was released on Friday with 15 Indians. The vessel was hijacked last year in September and we have not established whether ransom exchanged hands," Mwangura told Xinhua over telephone from Mombasa.
Mwangura said the hijack had occurred approximately 100 nautical miles southeast of Dar es Salaam in Tanzania.
The vessel is managed by OMCI Ship Management Pvt Ltd from Mumbai and is owned by Bitumen Invest As from Sharjah.
The Horn of Africa nation has been without a functioning government since 1991, and remains one of the world's most violent and lawless countries.