(Bloomberg) -- Blowouts in Australian coal processing times at Chinese ports are not unprecedented and the government is working with officials in Canberra and Beijing to clarify reasons for the current round of delays, Trade Minister Simon Birmingham said.

Processing times for Australian coal shipments have expanded to close to 40 days from about 25 days at some ports, he told Sky News’s Speers on Sunday program. Similar delays occurred late last year.

The delays have raised concerns that the Chinese government could be reacting to Australia’s ban on Huawei Technologies Co, roiling coal markets and weighing on the Australian dollar. The minister downplayed that notion, saying the countries have had good relations recently, though he does not swap “text messages full of emojis” with his Chinese counterpart.

China’s foreign ministry said Friday that there is no ban on Australian coal and that customs officials are stepping up efforts to analyze and monitor the quality and safety of imported coal. Chinese domestic issues including environmental concerns and protection of the local coal industry could also be at play, Birmingham said.

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