The Radiation and Nuclear Safety Authority, which is inspecting the foundation, says it's looking into how quality control was supervised and why it took six months for the Authority to be notified of the irregularities.
The private electricity generation company TVO is in charge of the construction project. It says the irregularities have no effect on the hardness or soundness of the concrete.
TVO is building the third reactor for the Olkiluoto plant, which already has two reactors. The one in construction will be Finland's fifth, and is likely to be completed in 2010. Construction was already behind schedule before the foundation had to be inspected.