Investigators at Societe Generale SA say they suspect former futures trader Jerome Kerviel was helped by an assistant to cover up massive trading positions that led to a multibillion dollar loss.

They say the French bank's management failures and culture of risk-taking were partly to blame for failing to spot the positions, which when they were unwound let to a loss of more than $7 billion.

Investigators didn't find any signs of embezzlement by Kerviel but say that he had sought to boost his results — and thus increase the amount of bonus he could hope for.

The findings came in two internal reports that the bank made public Friday — one led by a committee of independent directors, the other by audit firm PriceWaterhouseCoopers.