A Peruvian judge on Friday banned Repsol's Peru director and three other executives from leaving the country for 18 months while the government investigates an oil spill that occurred on January 15.

Peru authorities are investigating the Spanish firm Repsol following the oil spill, which was reported after surging waves caused by the eruption of an underwater volcano near Tonga.

Oil spill twice as big as previously thought

Environment Minister Ruben Ramirez told reporters that Peru had a "figure so far of 11,900" barrels, almost twice the 6,000 reported earlier.

Repsol's estimate puts the spill at 10,396.

Last week, Peru declared an environmental emergency and announced that 21 of its beaches had been contaminated by the spill.

The spill occurred when an Italian-flagged tanker was unloading oil at the La Pamilla refinery, 30 kilometers north of the Peruvian capital Lima.

Repsol said the tanker was hit by freak waves caused by a tsunami after an underwater volcano erupted in Tonga.

Prosecutors said the oil slick has been dragged by ocean currents about 140 kilometers north of the refinery, adding that this has caused the death of an undetermined number of fish and seabirds.

What are the charges against the Repsol execs?

Judge Romualdo Aguedo imposed the ban after considering there's a "potential risk" that Repsol's Peru director and three executives would leave the country.

Repsol has said that it's cooperating with the authorities in the investigation and working on cleaning affected beaches.

Peru has demanded compensation from Repsol, which faces a potential $34.5 million (€31 million) fine, Peru's Environment Ministry said.

Repsol's Peru director is accused of the crime of "environmental pollution to the detriment of the state," and the three executives are accused of being "accomplices."

On Friday, Peru's judicial authority authorized the seizure of the Italian-flagged tanker involved in the spill after a request was filed by the environmental branch of the Peruvian fiscal authority.

Repsol has said that the exact number of barrels spilled can only be confirmed after ascertaining the volume of oil still remaining in the tanks of the ship.

sdi/ (AP, AFP, Efe, Lusa)