Ahead of their highly anticipated and high-profile IPO, Twitter is reportedly looking to more than double their square footage in mid-Market with a second office right around the corner from their current digs at 1355 Market Street.

People with knowledge of the negotiations told Bloomberg that the social media giant is currently the only candidate looking to lease a 320,000 square-foot space at One 10th Street. The property is owned by Twitter's current landlord Shorenstein Properties LLC and will make up the second piece of Market Square — their name for the block between 9th and 10th Streets. The building at One 10th Street (or 1TENth Street, if you go by the developer's spelling) is expected to be complete by Summer 2014.

The company is expected to use some of the fresh cash from its upcoming IPO to expand quickly. If the deal happens, it will more than double the company's current square footage of 295,000 square feet and take up almost 95% of the 10-story office building on 10th Street. The remaining square footage would be left for ground-floor retail.

Twitter arrived in their mid-Market offices in the Summer of 2012 after a game of chicken with the city led to a sizable and controversial tax break for companies that stayed in town and helped spruce up the maligned stretch of Market Street. The tax break means employee stock options are exempt from the usual 1.5% payroll tax. The former S.F. Furniture Mart, now affectionately referred to by most as "The Twitter Building," also houses the offices of tech companies like One Kings Lane, Yammer and Square.

Previously: Twitter Announces IPO ... Via Twitter
Yoga Studio, Rooftop Garden, Micro-Health Kitchen: A Look Inside Twitter's New Headquarters
S.F. Approves Twitter Tax Break
[Bloomberg]