China’s exports of very-low-sulphur marine fuel rebounded 15% in May versus April as the country’s merchandise exports recovered, but still stood nearly 10% below the year-ago level, customs data showed on Monday.

Exports of very-low-sulphur fuel oil (VLSFO), measured mostly by sales from China’s bonded storage for vessels plying international routes, were 1.4 million tonnes, data from the General Administration of Customs showed.

That compared to 1.22 million tonnes in April and 1.55 million tonnes a year before.

China’s exports grew at a double-digit pace in May, beating expectations in an encouraging sign for the world’s second biggest economy, as factories restarted and logistics snags eased after authorities relaxed some COVID-19 curbs in Shanghai.

But limited refinery production of the marine fuel constrained its exports, analysts said.

Exports for the January-May period reached 7.68 million tonnes, down from 8.15 million tonnes in the same period of last year.

Fuel oil imports into bonded storage, including both high-sulphur and low-sulphur products, fell nearly 36% on the year to just over half a million tonnes.

Imports in the general trade category, however, nearly doubled from the year-ago level. Imports under this category, which is subject to a consumption tax of 1,218 yuan ($181.77) per tonne, are made by independent petrochemical firms and independent refiners as feedstock.

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The table below shows China’s fuel oil imports and exports, all in metric tonnes.

The column of exports under bonded storage trade largely captures China’s low-sulphur oil bunkering sales along its coast.