Satellite imagery has confirmed Iran's Sadra shipyard is building another aframax tanker, according to the investigative website Bellingcat.
It said that footage obtained by Planet Labs shows a vessel under construction at the island site.
The report said a keel was laid in April last year but little progress was made until November, the targeted month for the return of US sanctions.
The ship is likely to be destined for the domestic market.
The yard was previously building three aframaxes for Venezuela's PDVSA, but only one was completed.
Between November 2018 and January 2019, new sections of the latest tanker’s keel were laid in drydock, Bellingcat said.
These sections were originally part of PDVSA's second ship, but have been lying beside the dock since 2012.
Bellingcat said infrastructure upgrades at Sadra remain incomplete.
It claimed a Goliath crane set up in 2012 to help speed the delivery of the Venezuelan order has never been used.
More shipbuilding planned
Last October, the Iranian government said it was building three 113,000-dwt aframax tankers at the yard as part of a new 100-vessel shipbuilding plan.
Last year, PDVSA finally managed to take delivery of the completed tanker it ordered at Sadra 13 years ago.
IHS Ships Register and other databases indicated ownership of the 113,000-dwt Arita (ex-Sorocaima, built 2015) passed to Albanave, a subsidiary of the state oil major, in the second half of last year.
