Salesforce.com is expanding its downtown presence by leasing about 450,000 square feet in a high-rise building that’s set to open in 2015.

Mayor Ed Lee announced Tuesday that the company leased the entire new building at 350 Mission St. and also will expand its current offices at 50 Fremont St.

“Salesforce.com’s major expansion downtown proves once again that investor confidence is driving San Francisco’s economic recovery,” Lee said in a statement. “This will bring thousands of new jobs and anchor The City’s Transbay district as a leading destination for innovative companies.”

The company’s expansion comes after it halted plans in January to build its own 2 million-square-foot campus in Mission Bay, saying at the time that it would outgrow the site before construction was completed. It decided instead to lease more space.

By 2016, Salesforce will have 1.6 million square feet of office space in San Francisco, according to the Mayor’s Office.