PYONGYANG, North Korea — The United States government must make a formal apology to secure the freedom of two Americans who remain imprisoned in North Korea after the release this week of Jeffrey Fowle, North Korean legal experts said Thursday.

Although North Korea released Fowle, getting Matthew Miller and Kenneth Bae out of prison will likely require an official statement of apology and formal request for their release from Washington, according to two North Korean law experts who spoke to The Associated Press.

Fowle, who had not yet been tried in court, was flown out of North Korea on a U.S. military jet Tuesday after being detained for six months for leaving a Bible in a nightclub in the city of Chongjin, where he was visiting with a foreign tour group. North Korean state media said he was released after leader Kim Jong Un granted him a special pardon following “repeated requests” from President Obama.

“In order to return (Miller and Bae) to their country, the United States must make an official apology and request their release,” said Sok Chol Won, a professor of international law at Pyongyang’s Academy of Social Sciences.

In Washington, State Department spokeswoman Jen Psaki dismissed suggestions that the U.S. issue a formal apology to North Korea to secure freedom for Miller and Bae.