Iran has released the crews from two Greek oil tankers the Revolutionary Guard Corps seized in May, according to Iran International.

Iran released the 49 crew members from the ships after seizing the tankers in May in retaliation after the United States confiscated oil from a tanker carrying the Iranian flag near Greece, the Greek union of commercial ships' seafarers announced.

On Monday, a Greek shipping minister source stated that "a very serious effort has been under way for the return of the Greek crews [as soon as possible.]”

The ship’s crews were released and will soon be returning to their countries of origin. New crews will be hired for the tankers once they are also returned, Reuters reported.

The union said in a statement on its website that it was not sure when the tankers, the MT Prudent Warrior and Delta Poseidon, will be released by Iran.

The development came after Greece agreed at the request of the US to release 100,000 tons of oil seized by Greek officials at the behest of the US from Iranian tanker Lana in late August. The ship was originally seized by Greece in April and part of its cargo was taken by the US based on sanctions.

Iran’s foreign ministry would not confirm the release of the crew members.