China has reportedly rejected a large coal shipment from North Korea, one day after the North fired a ballistic missile.

According to sources in China on Wednesday, Wenzhou City in China’s Zhejiang Province decided earlier in the week to return 16-thousand-300 tons of North Korean coal, citing mercury levels that exceeded Chinese standards. 

The shipment is worth one million U.S. dollars and will soon be returned to North Korea's western port of Nampo.

The shipment arrived in the Chinese city last October, but the city’s quarantine authorities made the decision to return it according to recently strengthened regulations.

But as the decision came just a day after the North test-fired an intermediate-range ballistic missile, some observers say the action may be China's warning against Pyongyang's provocation.

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