Flight delays may be commonplace in the country. But the airport in Hangzhou, Zhejiang, offered an unusual reason for traffic disruption on Wednesday night: it said planes had to be grounded because of 'suspected UFO activities'. Airport authorities kept mum about whether any 'close encounters of the third kind' were involved, but said the closure of almost an hour was due to 'safety measures' invoked by air traffic controllers. 'We were told there was a possible unidentified flying object and therefore all take-offs and landings at the airport were halted,' a spokesman for Hangzhou Xiaoshan International Airport said. The initial advisory was issued at 8.45pm on Wednesday and the airport's runway remained closed until an all-clear signal was given at 9.41pm. 'Following that, normal services resumed,' he said. 'In total, six outbound flights and 12 inbound flights were affected by the closure.' He refused to speculate on the nature of the mysterious object, saying that an investigation had been launched into the incident by the General Administration of Civil Aviation of China in conjunction with the provincial government. The enigmatic incident has sparked off a flurry of stories in cyberspace with a number of websites and blogs posting photographs purporting to be the object in question. However, one image of the Hangzhou sighting reproduced on Xinhua's website appeared to suggest that rather than a visit from ET, it, too, could have had a terrestrial source. Instead of a flying saucer, the blurry and indistinct enlargement showed what appeared to be a large four-engined aircraft producing voluminous vapour trails caught in the evening sunlight.