HONGKONG immigration authorities breathed a sigh of relief yesterday as there were no reports of chaos at Lo Wu as tens of thousands of people crossed the border to China. The Immigration Department had been concerned about a repeat of last weekend's problems among the Ching Ming crowds as travellers waited for hours to cross the border. Figures show that 182,697 left Hongkong through various checkpoints on Thursday and 129,536 returned. Lo Wu was the busiest of the nine control points. Principal Immigration Officer Mr Ambrose Lee Siu-kwong blamed under-staffing on the Shenzhen side of the border for what he called ''temporary chaos'' last weekend. ''The major congestion was caused by overcrowding on the Chinese side,'' Mr Lee said. While Hongkong's Immigration Department had provided ''sufficient resources'', Shenzhen had left counters without staff, he claimed. Figures show that 190,375 people left Hongkong through various checkpoints yesterday and 122,670 returned. Lowu was the busiest of the nine control points, dealing with 125,000 people. Since April 1, about 1.43 million people had left Hongkong.