By Elise Labott, From CNN

Washington (CNN)An inactive Hellfire missile sent to Europe for training was inadvertently shipped to Cuba, where it has remained since 2014, sources familiar with the matter said Friday.

Hellfires are air-to-ground missiles typically fired from helicopters. Although initially designed as anti-tank weapons, they are often modernized and currently deployed from drones in anti-terrorism operations.

The missile wrongly sent to Cuba is called a Hellfire Captive Air Training Missile (CATM), a “dummy missile” used in exercises. Sources said that it contained an incomplete guidance section and was not fitted with a warhead, fusing system rocket monitor or operational seeker — all components needed to successfully hit a target.

But while it was not operational, the missile still contained sensitive American weapons technology, such as targeting and sensor information, that U.S. officials said would be concerning if it fell into the hands of adversaries. The Wall Street Journal first reported the missile’s location.

“This is an issue that the administration takes very, very seriously. I think for quite obvious reasons,” White House spokesman Josh Earnest said Friday when asked about the issue.

The sources said the U.S. has been trying for more than a year to get the Cuban government to return the missile. The delay could have been complicated by the attention paid to the historic thaw between the U.S. and Cuba last December, followed by the restoring of ties and opening of embassies in Washington and Havana this summer.

One source described the training missile as “fairly common” and noted that the U.S. just notified Congress this week of a sale of such dummy missiles along with active Hellfires to Iraq.

“The manufacturer shipped the dummy missile to Europe for a NATO training exercise in the summer of 2014,” the source said. The missile was sent to Spain for the exercise from Orlando, source said.

The sources said the State Department, which oversees the sharing of sensitive military technology with allies, approved a license for a temporary export. Under the Arms Export Control Act, this licensing is needed for any exports of such technology by U.S. companies.

During its return from Rota, Spain, to the United States, the sources said missile was misrouted by the cargo-shipping firm as it traveled from Madrid for its flight back to Florida. Instead of flying from Madrid to Frankfurt, Germany, and then back to Florida, the missile was misrouted to Paris and on to Havana.

Upon realizing the mistake, the company notified the U.S. government about the error as it was required to do under its export license. Sources said it is typically the responsibility of the company that holds the license to retrieve the lost article. The company, however, asked for help from the U.S. government because the missile was in Cuba, with which the U.S. has only recently restored ties and where direct flights between the U.S. and Havana do not currently operate under an aviation agreement between the two countries.

“The shipping was routine and by the book. When they became aware of the misrouting, they notified the State Department. Since then, they have actively cooperated in (U.S. government) efforts to both review the incident and to recover the item,” one of the sources said.

The source continued, “As warranted, the department may support the U.S. company’s corrective efforts in carrying out our general mission to further U.S. national security and foreign policy by assisting U.S. companies overseas and ensuring compliance with the applicable laws.”

David McKeeby, a State Department spokesperson, said that by law he couldn’t comment on defense trade licensing cases and compliance issues.

But he did say that “under the Arms Export Control Act, the Department licenses permanent and temporary exports by U.S. companies of regulated defense articles. U.S. companies are responsible for documenting their proposed shipping logistics in the export license as well as reporting any shipping deviations to the Department as appropriate.

The sources said the Department of Homeland Security is investigating to make sure the missile was not intentionally sent off course as part of an espionage or criminal operation, rather than just an accidental misrouting of the shipment. The Department of Justice, however, has the lead in the investigation.

CNN’s Jamie Crawford contributed to this report.

For more on this story and video go to: http://edition.cnn.com/2016/01/08/politics/cuban-missile-delivery/