OMAHA, Neb. (AP) -- The top bid for a private lunch with investor Warren Buffett is already approaching $400,000 and it's likely just starting to warm up, as the bidding often reaches astronomical levels near the end of the weeklong auction.

The winning bids have exceeded $2 million in four of the past six years, and in 2012 the auction winner paid $3,456,789.

The top bid Tuesday morning was $370,100.

Buffett is chairman and CEO of Berkshire Hathaway, and the 83-year-old is a prominent philanthropist.

The auction benefits the Glide Foundation, which provides social services to the poor and homeless in San Francisco.

Bidding continues until 9:30 p.m. CDT Friday.

The winner can invite up to seven friends to the lunch. The only topic off limits is what Buffett might invest in next.

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