Balfour Beatty will produce the venue for the swimming and diving events.And Team Stadium, which has already built Arsenal's Emirates Stadium, will construct the site for the athletics events as well as the opening and closing ceremonies.

　　The Olympic Delivery Authority said the cost of building the two venues were within its baseline budget of £6.09bn.A contractor for the Velodrome will be announced in the next few weeks.

　　The Aquatics Centre will have a capacity of 17,500 during the Games and it will include two 50-metre swimming pools and a diving pool - facilities London currently does not have.The budget for the centre is £242m, while a huge land bridge to the site will cost a further £61m.

　　The ODA said the total of £303m had not changed throughout the procurement process.Team Stadium, made up of Sir Robert McAlpine, HOK Sport and Buro Happold, built the Telstra Stadium in Sydney.The budget of £496m for the Olympic Stadium was published last October.

　　Announcing the contracts, ODA chief executive David Higgins said: "With these contracts signed there is a real sense of momentum.

　　"All of these venues will not only provide state of the art facilities for the Games but also provide permanent legacy facilities for elite and community use long after the Games have gone."Olympics minister Tessa Jowell added: "This is an important milestone and illustrates that the project remains firmly on track."