Beijing yesterday admitted cost overruns on some Olympic construction projects but says it remains confident that all venues will be completed by the end of this year as scheduled. Xu Bo, an official from Beijing's 2008 Projects and Construction Headquarters Office, said that the event organisers had paid close attention to some contractors who had problems controlling costs. 'Certain construction companies are having problems,' he said. 'Their actual spending [on certain projects] is higher than their expectations at the time of their bidding.' It is the first time the Olympics organisers have admitted having such problems. But Mr Xu insisted that the US$2 billion project to build or renovate the 31 venues for the Games remained on course and said the construction companies selected for the big projects would be able to fulfil their contracts. 'We are strengthening the supervision and regulation in terms of the venue construction and we are fully confident.' He said the authorities would strengthen control of expenses and noted that rising costs were 'risks inherent in a market economy'. Olympics organisers also announced that the government would spend about 12 billion yuan this year on cleaning and repainting about 20,000 old buildings and other facelift projects. Beijing Municipal Construction Commission director Sui Zhenjiang yesterday denied earlier state media reports that Beijing planned to clear the city of millions of migrant workers during the Games and said construction projects in the city would not be halted for the Olympics. He said migrants working on the Olympic venue sites had been given priority by the authorities in the campaign to ensure their wages were duly paid by sub-contractors. Mr Sui said construction projects would be allowed to continue despite concerns over their impact on already poor air quality.