After oil mysteriously washed ashore on some 2,100 kilometres of Brazil's coastline for two months, officials have finally identified a suspect: a Greek-flagged ship belonging to Delta Tankers Ltd.

Key points: The source of the oil has remained unclear since it started appearing in early September

The source of the oil has remained unclear since it started appearing in early September The Brazilian Government says there is "no indication of another boat", other than Delta's, that could have caused the spill

The Brazilian Government says there is "no indication of another boat", other than Delta's, that could have caused the spill The Greek firm has not responded to requests for comment

The Delta-owned NM Bouboulina was navigating through Brazilian waters at the time and location of the spill, Brazilian police and prosecutors said.

Brazil's Government has been striving to investigate the cause of the spill that has hit 286 beaches along the north-east coast and hurt fishing and tourism.

Officials have described it as one of the country's worst environmental disasters.

The specific source of the oil has remained unclear since it began appearing in early September.

In a search order seen on Friday (local time) by Associated Press, Brazilian prosecutors said "there is no indication of another boat" that could have discharged the Venezuelan crude into the sea.

The spill has been described as one of the country's worst environmental disasters. ( Reuters: Lucas Landau )

The same day, authorities in Rio de Janeiro coordinated a search at a maritime agency that has previously represented Delta, and the office of a crisis management consultancy.

Delta did not immediately respond to requests for comment submitted after business hours in Athens.

The 13-year-old Suezmax is among Delta's fleet of 30 tankers controlled by Greek shipping magnate Diamantis Diamantidis.

Oil was from Venezuela, Brazil says

The Brazilian Government has said the oil came from Venezuela after state-run oil company Petrobras identified three of the neighbouring nation's fields as the source of the crude.

The Bouboulina, named for a 19th century heroine of Greece's war of independence, docked in Venezuela on July 15 and departed three days later, according to the Brazilian search order.

At least 286 beaches along Brazil's north-east have been hit. ( Reuters: Adriano Machado )

The Venezuelan Government has previously denied its country is the source of the spilled crude.

From Venezuela, the tanker embarked with about 1 million barrels of Merey 16 crude.

It sailed past the north-east corner of Brazil en route to Cape Town, South Africa, and the Malacca coast of Malaysia, according to Kpler, a company that tracks seaborne commodities.

On September 3, off the coast of Malaysia, the vessel turned off its transponder signal for 10 days as it unloaded cargo, likely via a ship-to-ship transfer to an unknown vessel or vessels, Kpler said.

Ships are required to emit transponder signals but sea captains dealing in Venezuelan crude are increasingly turning off the safety device to help evade US sanctions that prohibit companies from buying crude from Venezuela.

Successive rounds of US sanctions have made it illegal for American companies to do business with the Government of Venezuelan President Nicolás Maduro.

The Brazilian Government has said the oil came from Venezuela. ( Reuters: Lucas Landau )

In August, the Trump administration hardened its stance further, warning foreign entities that they could see their US assets seized unless they cut ties to the socialist leader's Government.

A number of European oil companies, as well as Russia, India and China, are major buyers of crude from Venezuela's state-run oil giant, PDVSA.

All the companies rely on the US to process financial payments.

The ship responsible for the spill had been held in the United States for four days due to problems "in the system to separate water and oil for discharge into the ocean," Brazil's Navy said in a statement.

It did not provide more details.

A July 29 satellite image showed an oil spill 733 kilometres from north-eastern Paraiba state, the Navy said in a statement.

Following analysis of maritime traffic, the Navy added it detected that the ship was navigating in the region where the spill appeared and was headed for South Africa.

AP