LONDON — The cost of building the venues for the 2012 London Olympics has increased by $207 million in the last seven months.

That's according to figures released Wednesday after London Mayor Boris Johnson commissioned a high-level study last month. He was concerned about the global turmoil in the financial markets and the effect on the Olympic budget.

Since November, the cost of the 80,000-seat Olympic Stadium, which will be built by a consortium involving Sir Robert McAlpine, HOK Sport and Buro Happold, has risen from $976.2 million to $1.02 billion. That includes the price of converting the stadium to a 25,000-seat athletics venue after the games.

"Containing cost pressures and avoiding further calls on the contingency will be difficult and require sustained effort to manage contractors effectively," said the report by business tycoon David Ross. "This process must be overseen from the top by the Olympic Board on the basis of the best possible information."

The overall cost of the Olympics — including regeneration of a rundown East London area into an Olympic Park — has been projected at $18.2 billion.