Alibaba.com slumped 17.47 per cent yesterday as investors dumped their shares to lock in profit after the massive first-day gain on Tuesday, market watchers said. The stock shed HK$6.90 to close at HK$32.60 on a turnover of HK$6.3 billion. It was the second-biggest loser after Sam Woo Holdings, which plunged 26.04 per cent. The mainland's largest e-commerce portal touched HK$40.50 shortly after the market opened but soon began its retreat, falling past its previous close of HK$39.50 amid heavy selling by retail investors. The decline cut Alibaba's market value to HK$164.7 billion at yesterday's close from HK$199 billion on Tuesday when the stock surged 192.59 per cent on its first trading day on the market. Alibaba's debut on Tuesday tested the capacity of the Hong Kong stock exchange's electronic system to execute massive order volumes in a short period of time. Some investors complained about slow execution of their orders. Moses Cheng Mo-chi, a director of Hong Kong Exchanges and Clearing, said the system could handle large transaction volumes despite some 'traffic congestion' on Tuesday. Mr Cheng said it was inevitable that the system would face challenges when trading demand suddenly surged. However, the exchange had been updating and improving the system to cope with more transactions, he said.