TEHRAN (IRNA) — Iran released on Friday a South Korean ship and its captain detained since January after South Korea promised to try to secure the release of Iranian funds frozen in South Korean banks under U.S. sanctions, a South Korean official said.

Iran’s Ministry of Foreign Affairs has announced that the Islamic Republic released a South Korean oil tanker following an investigation, which led to a decision that the ship and its captain have not had bad record.

Saeed Khatibzadeh, Spokesman for Iran’s Foreign Ministry, told reporters on Friday that the chemical tanker, Hankuk Chemi, was released after an investigation into environmental pollution, and at the request of the South Korean government and its owner.

The Islamic Revolution Guards Corps seized the Korean oil tanker and the 20 crew members in Iranian waters on January 4, 2021, accusing the ship violateng environmental regulations. A few days later, Iran released all crews except for the captain. Iran has denied allegations that the seizure of the tanker and its crew constituted hostage-taking, saying it was South Korea that was holding Iranian funds hostage.