Maguire Properties Inc., the biggest office landlord in downtown Los Angeles reported a net loss of $299 million on Tuesday.

The company also said it was in discussions to extend debt terms on several of its buildings.

The latest quarterly result represents a loss of $6.17 per share, compared with a net loss of $2.02, or $96 million, for the fourth quarter of the previous year.

The company attributed the losses to write-downs of the value of its properties. Two properties that it sold during the quarter, Griffin Towers and 2385 Northside, had combined impairment charges of $100 million. The rest of the Maguire portfolio had a cumulative impairment charge of $164 million.

In a Tuesday morning conference call, Chief Executive Nelson Rising said the company was in discussions to extend loans on buildings in Irvine and Glendale.

The loan on the six-story, 150,000-square-foot Park II office building in Irvine matures in May. The loan on its Glendale holdings matures in June. Rising said the company may sell the buildings as an alternative to loan extensions.

Rising also plans to negotiate a loan extension on Plaza Las Fuentes, an eight-story office building and hotel in Pasadena. Its loan matures in September.

Shares of Macguire increased 13 percent, or 35 cents, to trade at $3.02 by mid-day on the New York Stock Exchange.