MNA � Iranian Road Minister Mohammad Eslami said on Wednesday that "the black box of the downed Ukrainian plane, as one of the main items of studying the incident, must remain in Iran."

He further described that in case of any problems with decoding the black box, required decisions will be made to ask the other involved sides for help.

"The black box is an inseparable item of the incident and since the crash has taken place in Iran, according to Annex 13 of International Civil Aviation Organization (ICAO), Iran Civil Aviation Organization is in charge of investigations," he said.

"A delegation has also traveled to Ukraine to study the documents of the airplane," he added.

Informing about his recent trip to Ukraine, Eslami said he has conveyed condolences of Iranian President to the Ukrainian President and nation, while the other side expressed gratitude for Iran's cooperation on the issue.

Heading an Iranian delegation, Eslami traveled to Kyiv on Monday to meet and hold talks with Ukrainian President Volodymyr Zelensky and Foreign Minister Vadym Prystaiko on the unintentional downing of the Ukrainian plane.

In a phone conversation on Thursday evening, Iranian and Ukrainian foreign ministers discussed the latest situation about the unintentionally-downed Ukrainian airplane.

During the phone talk, Mohammad Javad Zarif voiced Iran's readiness for handing over the bodies of Ukrainian nationals of Ukraine's 737 plane victims and allowing that country's experts to be involved in examining the black box.

Iran has urged all parties involved, including American multinational aviation corporation Boeing, to contribute to a probe into a Ukrainian plane crash near the capital Tehran that killed all 176 people aboard on January 8.