On Wednesday, the market regulator suspended trading in the shares.
In turn, the Italian stock market regulator, Consob, opened an inquiry.
The Italian government later this week will consider proposals to strengthen the country's stock market regulator.
Porsche's options transactions are being investigated by the German market regulator BaFin.
Alain Bichsel, a spokesman for the market regulator, declined to identify the affected institutions.
The French finance minister, Francis Mer, inaugurated the new financial market regulator in Paris.
Britain's market regulator, the Financial Services Authority, is also participating in the A.I.G. inquiry.
Consob, the Italian market regulator, is investigating whether BPL and its allies acted in concert.
The French market regulator said its ban could last until Nov. 11.
Ramesh Abhishek, India's chief commodities market regulator, said guar trading would resume when supplies proved adequate.
On July 27th Consob, Italy's market regulator, suspended BPI's bid for Antonveneta as a "precaution".
