Italian stock market regulator Consob has been calling stockbrokers in Milan in an attempt to find out who is behind the heavy trading in shares of Ing C Olivetti & Co SpA, Reuter reports. The shares been on a roller-coaster ride in recent days, plunging after former chairman Carlo De Benedetti resigned at the beginning of the month and sharply rebounded when Francesco Caio was pushed out last week and replaced by Roberto Colaninno – despite the fact that he says it will take a month for him to make any decisions on the future direction of the company, damagingly extending the uncertainty. That view was uppermost on Friday and the shares were back on the slide; it was 5.92% off at 534 lire at 3pm.