Mexico's state oil firm has vowed to get to the bottom of accusations that the Brazilian construction and engineering group may have paid bribes to the company.
Prosecutors signed an agreement that seeks to coordinate and expedite the investigations into the firm's activities.
Pampa acquired controlling stakes in each during 2016.
The pipeline expansion will bring natural gas to 104,500 homes across four provinces.
Authorities also kick off public consultation for a biofuel promotion initiative.