A US National Guard helicopter with six people on board has crashed off the coast of Puerto Rico, a military spokesman said yesterday.

It remained unclear why the UH-72 helicopter went down while flying along the northern coast of the US territory, Major Paul Dahlen, a spokesman for the National Guard in Puerto Rico, said.

The US Coast Guard and Puerto Rican authorities were searching for those on board, including three crew members, two government officials and a military official, he said.

The UH-72 Lakota, a military version of the EC145 Eurocopter produced by European aerospace firm EADS, is often used for medical evacuations and transport and logistical missions.

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