Another U.S. mall landlord could be facing activist pressure.
Macerich shares jumped more than 12 percent Thursday afternoon on the news.
Representatives from Third Point and Macerich didn't immediately respond to CNBC's requests for comment.
Third Point now owns nearly 5 percent of the California-based REIT and could push for a potential sale, among other changes, sources told Bloomberg.
Macerich was last targeted by activist investors in 2015, when Jonathan Litt's Land & Buildings Investment Management and Orange Capital built a position in the company. At the time, Macerich had just rejected a near $17 billion takeover bid from REIT rival Simon Property Group.
Macerich currently owns 54 million square feet of real estate, consisting primarily of interests in 48 regional shopping centers, according to its website.
In 2017, the retail real estate industry has increasingly faced pressure from outsiders, as news of retail bankruptcies and store closures threatens the future health of their properties. More shoppers are ringing up purchases online, forcing mall owners to think outside the box when renovating vacated spaces.
"Despite recent, well-documented, bankruptcies of certain traditional retailers, few of which have come as much of a surprise, Macerich achieved solid re-leasing spreads and tenant sales growth," Chief Executive Arthur Coppola said when the company reported earnings last month.
In regard to Loeb's investment strategy , Third Point materials describe its philosophy as "event-driven, value-oriented," with an "emphasis on special situation equities." The firm "seeks to identify situations where we anticipate a catalyst will unlock value."
Third Point had $18 billion of assets under management as of late June.
According to Bloomberg, it's still unclear if there have been talks between the activist investor and Macerich.
Even with Thursday's gains, Macerich's stock has lost a little more than 10 percent in 2017.
— CNBC's Tae Kim contributed to this report.