A Peruvian judge banned Repsol's Peru director and three other executives from leaving the country for 18 months while the government investigates an oil spill at a refinery run by the Spain-based company.

Peru authorities are investigating Repsol following the oil spill on Jan. 15, which was reported after surging waves caused by the eruption of an underwater volcano near Tonga.

Peru declared last week an environmental emergency after announcing that 21 beaches on its Pacific coast were contaminated by the spill. Prosecutors also opened an investigation for the crime of environmental contamination.

Peruvian authorities on Friday raised the estimate of the size of the spill to at least 11,900 barrels and said that figure could rise. Repsol put the spill at 10,396 barrels. The earlier estimate had been at least 6,000 barrels.

Judge Romualdo Aguedo imposed the ban after considering there's a "potential risk" that Repsol's Peru director, Jaime Fernández-Cuesta, and three executives would leave the country. The company has said that it's cooperating with the authorities in the investigation and also working on the cleaning of the beaches affected.

Repsol hired more than 2,000 people, including local fishermen, to clean the beaches. The company has also promised to deliver food baskets to affected families.