April 29 (Reuters) - Oil and gas firm Diamondback Energy said on Monday it had received a second request from the U.S. Federal Trade Commission (FTC) in connection with the $26 billion deal to buy privately-held Endeavor.

The U.S. antitrust regulator has asked for additional information and documentary material as part of its review of the proposed merger.

CONTEXT

Midland, Texas-based Diamondback had said in February it would buy privately held rival Endeavor Energy Partners in a cash-and-stock deal, which is expected to close in the fourth quarter.

The combined company would be the third-largest oil and gas producer in the Permian Basin of West Texas and New Mexico, behind Exxon Mobil and Chevron.

U.S. lawmakers have sought increased scrutiny of multi-billion dollar deals in the oil and gas industry from the FTC.

WHY IT IS IMPORTANT

This is the fifth oil and gas deal since December to get a second request from the FTC. Other deals to receive second notices include the Exxon - Pioneer, Chevron - Hess and Occidental - Crownrock .

Earlier this month, Chesapeake Energy and Southwestern Energy said the closing date of their proposed $7.4 billion merger had been pushed back to the second half of the year after receiving a second request for information from the FTC.

BY THE NUMBERS

The combined Diamondback-Endeavor company would pump 816,000 barrels of oil and gas per day (boepd), behind the Exxon-Pioneer combination of about 1.3 million boepd and Chevron's 867,000 boepd in the basin. (Reporting by Tanay Dhumal in Bengaluru; Editing by Tasim Zahid)