Former Massachusetts House Speaker Salvatore DiMasi has again pleaded not guilty to federal corruption charges.

DiMasi and three co-defendants entered the pleas Thursday during their arraignment on an expanded indictment adding extortion to earlier public corruption charges.

The original indictment alleged DiMasi and three associates rigged two lucrative state contracts for the software company Cognos in exchange for payments, with the former speaker pocketing $57,000.

A superseding indictment handed up last month added the extortion charge. It says DiMasi accepted payments from Cognos and a second member of the scheme, Joseph Lally, knowing the money was in exchange for helping the Burlington, Mass.-based firm win the contracts.