RIO DE JANEIRO >> Brazilian authorities said today that they have no way of knowing how much more oil will wash ashore the country’s northeastern coast, despite President Jair Bolsonaro’s ominous warning during a Sunday night TV interview that “the worst is yet to come.”

In the interview, Bolsonaro also stuck to the government’s assertion that a Greek freighter caused the oil spill scattered across beaches along 1,300 miles of coastline even after the shipowner’s denial of any leakage from its vessel.

“All signs point to this Greek cargo ship. All of them,” he told Record TV, adding that the leak, “by all accounts looks like it was criminal.”

Brazil’s government has been striving to investigate the cause of the spill that has hit 321 beaches along the northeast coast since early September, hurting fishing and tourism. Authorities have described the spill as one of the country’s worst environmental disasters.

The crude’s density renders it invisible from above, making it hard to track its origin or to have a clear picture of the amount of oil yet to reach Brazil’s coast.

About 4,000 tons of oil has been collected from northeastern beaches thus far, according to a statement Sunday from the Navy, Brazil’s environmental regulator, and the national petroleum agency.

“To say how much oil there still is very difficult to say,” Commander Leonardo Puntel of the Brazilian Navy said at a news conference today. “Since the oil is underwater, we don’t know if there’s still a lot or a little. There is effectively no correct and accurate way to monitor these oil spots,” he said, adding that they have seen a decrease in oil arriving onto beaches in recent days.

He called the disaster “unprecedented.”

“There is no case in the world of a large-scale oil spill where the origins are totally unknown. This case has no parallel, we don’t know who polluter is,” Puntel said.

Brazil’s defense minister, Gen. Fernando Azevedo e Silva, also stressed how challenging it is to calculate the spill’s scope.

“It is not detectable by satellite. … It is imperceptible. We do not know how much will still come,” he said.

David Zee, an oceanographer at the State University of Rio de Janeiro, said that the 4,000 tons of collected oil is “just the tip of the iceberg,” both because the cleanup effort is mostly limited to sandy beaches in populated areas and also because a large portion of spilled oil is likely spread deep beneath the ocean’s surface.

Furthermore, when currents bring oil to sandy shores, it is relatively easy to collect, while is nearly impossible to remove from corals and mangrove forests, which make up part of the affected area, Zee said.

Brazilian prosecutors have named Greek shipping company Delta Tankers Ltd as a suspect of the leak’s origins. The company issued a statement earlier saying it found no evidence of leakage after reviewing the ship’s cameras and sensors.

“This material will be willingly shared with Brazilian authorities, should they contact the company regarding this investigation. So far, no such contact has been made,” the statement said.

Federal Police officer Franco Perazzoni said at today’s news conference that the company will be officially notified via Interpol.

Brazilian prosecutors said previously that Delta’s oil tanker, named Bouboulina, was navigating through Brazilian waters at the time and location of the spill. The ship was carrying oil from Venezuela to Malaysia.

In a search order seen Friday by The Associated Press, Brazilian prosecutors said “there is no indication of another boat” that could have discharged the Venezuelan crude into the sea.

Brazilian armed forces along with environmental protection agencies and petroleum authorities are leading an operation to clean, monitor and investigate the oil spill. Several public universities are conducting research about the spill’s origins and impact. Television footage has also shown volunteers flocking to beaches to help with the cleanup, often without government supervision.

Of particular concern at the moment is the Abrolhos national marine park, home to Brazil’s largest coral reefs. Authorities said Sunday night that they had removed the fragments of oil that had appeared in the park and so far no new traces had been found.

“A very small amount of oil arrived on Nov. 2, on Nov. 3 only a few fragments remained, today there’s none,” Puntel said at the news conference. “Will more oil fragments come? Maybe.”