UPDATED, Feb. 11, 12:41 p.m.: PricewaterhouseCoopers, the largest of the “Big Four” auditing firms, is expanding beyond its Madison Avenue headquarters to some 250,000 square feet at Vornado Realty Trust’s 90 Park Avenue, The Real Deal has learned.

PwC is finalizing a deal to take a large block of space on the lower floors of the 41-story, 1 million-square-foot office tower just south of Grand Central Terminal, according to sources familiar with the deal.

Asking rents in that part of the building are in the high $60s to low $70s per square foot.

The accounting firm’s New York headquarters is at Brookfield Property Partners’ 300 Madison Avenue, where it has about 800,000 square feet. Tim Dempsey at CBRE, who was part of a team that represented PwC in its lease at that property, is also negotiating on its behalf at 90 Park. An in-house team at Vornado is representing the landlord.

A representative for Vornado declined. A spokesperson for PwC said the company is exploring its options in the market, and only comments on signed leases.

PwC, which had revenues of $35.4 billion in 2015, had been looking to expand to a new space for some time, sources said.

Vornado recently overhauled the property, which is located between East 39th and East 40th streets. The real estate investment trust redid the lobby and made other upgrades to the tune of $30 million. A portion of the space PwC is taking was vacated by Capital One.

Professional service firms have been accounting for a slightly smaller slice of Manhattan’s leasing activity over the past three years. The sector accounted for 17 percent of leasing last year, according to research from Newmark Grubb Knight Frank. That’s down from 18 percent the previous year and 20 percent of Manhattan leasing in 2013.

This post was updated to include the name of PricewaterhouseCoopers’s broker, and a comment from PwC.