A mystery structure under construction next door to the Flint Center on the De Anza College campus in Cupertino. (CBS)

CUPERTINO (KPIX 5) — The mystery behind Apple’s new product launch announcement on September 9 is deepening with the building of a secretive structure at the site of the planned announcement next month.

Security guards on Thursday were shooing people away from the three-story tall structure, which is wrapped completed in white.

Forklifts hauling huge wooden boxes and semi trucks were seen going in and out of the structure being built next to the Flint Center on the campus of De Anza College in Cupertino, just a few miles from Apple’s headquarters.

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The Flint Center, where late Apple CEO Steve Jobs first debuted the original Macintosh computer in 1984, seats 2,300 people – a much bigger venue than the places Apple usually uses to show off its new products.

“Amazing how it all started in Silicon Valley and it’s crazy to think that this is where I’m from, this is where Apple started,” said De Anza College student Julie Du.

Apple is preparing for the big event in dramatic fashion. Security is tight at De Anza College and guards are posted at every corner surrounding the venue.

The company’s vague invitation, simply the date of the event printed with the words, ‘wish we could say more’ only adds to the mystery.

“There aren’t a lot of hints in the invite about what we’re going to see,” said CNET Senior Writer Shara Tibken.” It was a little more coy than a lot of them have been.”

Apple is expected to announce a new, larger iPhone at the September event and possibly a computerized watch.