(Adds Maguire's denial of Winthrop's request to buy preferred shares, updates with closing stock price)

By Ilaina Jonas

NEW YORK, April 13 (Reuters) - The New York Stock Exchange asked Maguire Properties Inc (MPG.N: Quote, Profile, Research) on Monday to explain why its stocks are soaring, but Maguire, one of the biggest office landlords in Southern California, declined.

"The Exchange has contacted the company and requested that the company issue a public statement indicating whether there are any corporate developments which may explain the unusual activity," the exchange said in an email, after Maguire shares soared more than 92 percent to an intraday day high of $1.73.

"The company stated that its policy is not to comment on unusual market activity or rumors," the Exchange said.

Maguire shares closed at $1.25, up 35 cents, or 38.9 percent. After the close of the market, Winthrop Realty Trust (FUR.N: Quote, Profile, Research) said Maguire's board declined to issue a waiver that would have allowed Winthrop, a real estate investment and loan company, to acquire up to 25 percent of Maguire's 7.625 percent Series A Cumulative Redeemable preferred stock.

Winthrop controls 9.45 percent of Maguire's common shares, according to a filing with the U.S. Securities and Exchange Commission.

Winthrop shares closed down 2 cents, or less than 1 percent, at $9.06. (Reporting by Ilaina Jonas; Editing by Brian Moss and Andre Grenon)