Google Inc has signed a deal to buy a huge Manhattan building, where it is a tenant, for $1.8 billion in one of the largest sales of a single building this year, according to a person close to the transaction.

Google, was the winner of a competitive bid for property, owned at 111 Eighth Ave. in Manhattan's Chelsea neighborhood, said a source familiar with the deal, but who was not authorized to speak publicly. The price comes down to about $600 per square foot.

Google could not be reached immediately.

The world's dominate Internet search engine occupies about 20 percent of the 2.95 million square foot building, which is owned by Taconic Investment Partners, the New York State Common Retirement Fund and German investment group Jamestown Properties.

The building last changed hands in 1998, the source said.

It was originally developed as the headquarters of the Port Authority of New York and occupies an entire square block between Eighth and Ninth avenues and 15th and 16th Streets. It is the second largest building in New York City.

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