The mainland's export growth last month may be too good to be true, with economists unanimously linking the strong performance to speculative fund inflows betting on yuan appreciation.
The situation adds to the complexity in reading the country's real economic strength.
Exports data has repeatedly beaten market expectations in recent months, in contrast to broad-based weakness in trade reported by economies in the region, including Taiwan, South Korea and Hong Kong.
The foreign exchange regulator has recently tightened rules on capital inflows management.
Last month, export rose 14.7 per cent from a year earlier, sharply higher than market expectation for a 9.2 per cent increase and 10 per cent growth in March, customs data showed.
Imports increased 16.8 per cent, compared with a 14.1 per cent growth in March, as companies stepped up purchases of commodities, supporting economists' view that a modest economic recovery was on the way.
China recorded a trade surplus of US$18.2 billion last month, reversing a deficit of US$900 million in March.
The yuan climbed to a 19-year high as the central bank strengthened the daily fixing to a record and exports topped analysts' estimates.
Overseas capital has continued to flow into the mainland to take advantage of an interest rate gap with western nations and yuan appreciation.
Economists widely believe that many exporters have moved goods into and out of bonded areas as well as Hong Kong, an international trade transfer hub, to forge trade deals.
The mainland's exports to Hong Kong jumped 57.2 per cent last month, even though shipments to its two largest trade partners - the United States and the European Union - both fell.
After adjusting various irregularities, the Royal Bank of Scotland estimated that China's exports might have actually gained only 5.7 per cent in US dollar terms, held back by "depressed global demand as well as the substantial exchange rate appreciation in recent months".
Throughput figures also trailed the strong export growth.
In the first quarter, container throughput at Shanghai port, the mainland's largest, climbed just 3.6 per cent year on year, while that in Shenzhen, the second-largest, rose 4 per cent.
The mismatch in different data has aroused the attention of the authorities. The Ministry of Commerce and the customs bureau both pledged to investigate potentially fake deals.
On May 5, the State Administration of Foreign Exchange issued a notice to require that banks' net foreign exchange positions be restricted by their onshore foreign exchange loan-deposit ratio.
They also vowed to strengthen scrutiny on any suspicious currency transactions.