OMAHA, Neb. -- Warren Buffett's company now owns 8 percent of Seritage, the real estate investment trust Sears created.

Berkshire Hathaway said in a filing with the Securities and Exchange Commission Thursday that it owns 2 million shares of Seritage.

The new stake would have been worth about $70 million at Wednesday's closing price. Seritage shares jumped $5.14, or 14.6 percent, to $40.37 after the investment was disclosed Thursday. That made Berkshire's stake worth nearly $80 million.

The documents Berkshire filed don't state whether Buffett made the decision to invest in Seritage.

But the relatively small size of the investment -- by Berkshire standards -- suggests one of the company's other investments made the move.