Strong buying demand in Metro City, Tseung Kwan O, prompted Henderson Land Development to put an extra 12 units on sale yesterday, raising the total number to 280. The move came amid estate agents' comments the popularity of the development was waning as prices overtook those in the secondary market. Henderson sales manager Donald Cheung said the company was 'very satisfied with the response'. He said the 273 units on offer had been snapped up. The average price on lump-sum sales was $4,698 per square foot - an increase of 7.3 per cent on the previous $4,380 per square foot. All units on sale were in block two, ranging in sizes from 510 square feet to 732 sq ft. Henderson last week registered about 1,800 buyers for yesterday's sale. A Midland Realty Tseung Kwan O branch staff member said compared to previous sales, the response for Metro City was mediocre following the price increase. In contrast, he said, prices for the district's other developments in the secondary market were comparatively lower - about $4,400 per square foot. As a result, the number of transactions in the secondary market had increased, he said. Last month, Henderson sold 800 units in one day with the most expensive units selling for more than $4,800 per square foot - up more than 16 per cent on the $4,110 per square foot pitched for the first 68 units on offer. The first phase of the Metro City development consists of six towers with 2,048 units, each measuring between 487 and 909 sq ft. Henderson had said it expected to generate between $6 billion and $7 billion if all the units sold. The project has attracted thousands of visitors to Tseung Kwan O. Developed in three phases, Metro City will include 21 residential towers with a total of 6,800 units. The project is expected to be completed by 2001.