A satellite image showing suspicious steam may indicate that North Korea might have restarted a nuclear rector capable of producing weapons-grade plutonium.

“The white coloration and volume are consistent with steam being vented because the electrical generating system is about to come online, indicating that the reactor is in or nearing operation,” said a statement from the US-Korea Institute at Johns Hopkins School of Advanced International Studies.

It is believed the Yongbyon Reactor can produce six kilos of plutonium per year.

The US State Department is not commenting on the satellite image other than to reiterate that Pyongyang's “nuclear program remains a matter of serious concern.” 

Washington wants Pyongyang to comply with a 2005 aid-for-disarmament agreement signed by North Korea, its neighbors and the United States.  Under that pact, Pyongyang should have dismantled its nuclear program in exchange for economic and energy aid.