Washington (CNN) New indicators, including satellite images, show that North Korea could be in the midst of building new missiles, the Washington Post reported Monday, citing officials familiar with the intelligence.

According to The Post, the officials said the new information reveals that work is potentially taking place on one or two liquid-fueled intercontinental ballistic missiles in Sanumdong, a suburb of Pyongyang.

Liquid-fueled rockets are harder to store and move than solid-fuel rockets because the fuel is more volatile, according to experts. The volatility of liquid fuel can cause missiles to fail in launch and the fuel has to be stored separate from the missiles, causing a decrease in military readiness. Liquid fueling can also take a fairly long time to complete, giving US spy satellites a period of time to see launch preparations underway. Solid-fueled missiles can be very quickly launched giving the US very limited warning

The National Security Council declined to comment when reached by CNN.

News that the North Koreans are potentially developing new weapons would be a heavy blow to President Donald Trump's efforts at diplomacy with North Korean dictator Kim Jong Un.

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