HOUSTON, May 15 (Reuters) - U.S regulators asked LNG exporter Venture Global LNG to update its emissions analysis for its proposed Calcasieu Pass 2 LNG export project in Louisiana, according to a letter sent on Wednesday.

Venture Global is seeking permission from the Federal Energy Regulatory Commission to double the capacity of its Calcasieu Pass liquefaction plant with a second phase that would produce 20 million tons of LNG per year.

The Arlington, Virginia-based company has given other regulators different emissions information on its CP1 project, FERC said, asking for updated emissions data following a complaint from environmental groups.

Last month, the Sierra Club told FERC that Venture Global LNG applied to Louisiana's Department of Environmental Quality (LDEQ) for a modification of its emissions permit to reflect higher levels of atmospheric discharge.

The expected increased emissions stemmed from proposed operational changes to that facility’s five combined-cycle combustion turbines, FERC said in its letter.

In response, Venture Global said that at the time it applied to FERC for approval to construct the CP2 plant, its application with the LDEQ was pending, and it has not received a greenlight.

Venture Global said the application reflected proposed operational changes involving increased hours of operation of the duct burners, but said emissions cumulatively would remain within air quality standards.

The LDEQ application for increased emissions was for CP1 and not for CP2, Venture Global added. (Reporting by Curtis Williams in Houston; Editing by Leslie Adler and David Gregorio)