PLEASANTON -- Workday plans a major expansion in Pleasanton by constructing a large new office building that could have up to 2,100 employees, city officials said Wednesday.

The software company hopes to build a six-story, 430,000-square-foot office building on 6.9 acres of vacant land it is negotiating to buy from BART. The new offices would be next to Workday's current headquarters near Stoneridge mall.

"We are really excited that Workday sees an opportunity to grow and expand and maintain their headquarters presence in Pleasanton," said Pamela Ott, the city's economic development director. "More Workday employees will be living, shopping, eating in Pleasanton. And there should be more hotel visits as customers visit Workday."

Workday, which offers Web-based business software primarily for human resources, currently occupies more than 250,000 square feet in Pleasanton and employs more than 1,400 people, said company spokesman Eric Glass.

In addition to its new planned building, Workday may eventually expand into a five-building office complex known as Stoneridge Corporate Plaza that is next door to its headquarters. Workday co-founder David Duffield, through a company he controls named NPC Holdings, bought that complex a year ago, but it is currently occupied by other tenants. It potentially could provide enough space for an additional 3,000 workers.

Pleasanton-based Workday launched an initial public offering in October 2012, raising $637 million through the first-time sale of its stock, which was priced at $28. On Wednesday, Workday's shares closed at $92.59, up 231 percent from the IPO price.

Workday is still losing money. However, for its 2014 fiscal year that ended in January, it generated revenue of $468 million, up 71 percent from the year before.

"Workday could have leased some of the older buildings in the area, but they chose to construct a brand-new building that meets the standards of what young tech engineers want," said Edward Del Beccaro, a managing director with Transwestern, a commercial realty brokerage.

This expansion also bodes well for the ongoing efforts by the East Bay to attract more tech companies.

"Workday shows that the Tri-Valley has the kind of tech engineers who can work for this kind of a company when they expand," Del Beccaro said. "The Tri-Valley is getting more tech jobs."

Contact George Avalos at 408-859-5167. Follow him at Twitter.com/georgeavalos.