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KUALA LUMPUR, Malaysia (CBSDFW.COM/AP) — Police in Malaysia say the half brother of North Korea’s leader who was killed in a Kuala Lumpur airport more than a week ago had a nerve agent on his eye and his face.

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The inspector general of police says a preliminary analysis from the Chemistry Department of Malaysia identified it as “Vx nerve agent.”

The substance – also known as ethyl N-2-Diisopropylaminoethyl Methylphosphonothiolate – is classified by the United Nations as a weapon of mass destruction.

Kim Jong Nam died Feb. 13 shortly after two women put a substance on his face while he was checking in for a flight.

Malaysia’s national police chief Khalid Abu Bakar says help has been sought from Interpol to issue an alert for the four North Korean suspects who left Malaysia on the same day Kim Jong Nam was killed.

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It is not known what Interpol can do, as the four are believed to have traveled back to Pyongyang and North Korea is not a member of Interpol.

Khalid also said there were no plans to send officers to Macau to collect a DNA sample from Kim Jong Nam’s family. Kim had a home in Macau and was about to fly there when he was killed.

North Korea says Malaysia’s investigation into Kim Jong Nam’s death is full of “holes and contradictions” amid speculation that its agents masterminded his assassination.

The Korean Jurists Committee said in a statement Thursday that the Malaysian investigation lacks fairness and has been influenced by the South Korean government, which blames Pyongyang for the death.

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The North has not acknowledged that the dead man is Kim Jong Nam. Thursday’s statement described him only as a North Korean citizen bearing a diplomatic passport.