U.S. regulators have made a second request for information about Kinder Morgan Inc's planned takeover of natural gas pipeline company El Paso Corp, a regulatory filing said on Wednesday.

The Federal Trade Commission has asked El Paso and Kinder Morgan for more information on the deal that will combine the two largest natural gas pipeline companies, and both are complying with the request, filings with the U.S. Securities and Exchange Commission said.

The request will extend the waiting period under Hart-Scott Rodino, but the deal valued around $21 billion is still expected to close in the second quarter of 2012, the companies said.