Imperial College London is set to appoint architects to extend Norman Foster's £27m Tanaka Business School at its South Kensington campus.

Sources close to the scheme said that six signature architects, thought to include Foster and Partners and Alsop Architects, would present their schemes for the extension at the end of March.

The college, which spends about £100m a year on construction, has recently used a number of high-profile firms including Sheppard Robson, Swanke Hayden Connell and Kohn Pedersen Fox.

However, it declined to reveal which other firms were involved in the competition.

The news follows the start of work on a £48m Laing O'Rourke scheme to build a hall of residence, designed by KPF, at neighbouring Princes Gardens.

The building is part of an overhaul of the square that also includes a £17.7m sports hall and swimming complex.

Foster's Tanaka Business School, built by ISG InteriorExterior, was completed in April 2004 after being funded by a donation from former student Gary Tanaka.

It fronts Exhibition Road, where a pedestrianisation scheme has been proposed to improve the area around the university and major museums such as the Science Museum and the Natural History Museum.