(Reuters) -The U.S. Federal Trade Commission is probing executives from major oil firms, including Hess Corp, Occidental and Diamondback Energy over their communications with OPEC officials, Bloomberg News reported on Friday, citing people familiar with the matter.

Agency investigators are looking for evidence of executives attempting to collude with OPEC officials on oil market dynamics, the report said.

Earlier this year, FTC barred former Pioneer Natural Resources CEO Scott Sheffield from Exxon's board on allegations that he attempted to collude with OPEC to raise oil prices.

The FTC made the move as it approved Exxon's $60 billion purchase of Pioneer.

Hess and Occidental did not immediately respond to Reuters requests for comment.