He’s back.

According to CNBC‘s Jim Goldman, at least two Apple AAPL  employees have told him they saw Steve Jobs at the company’s Cupertino, Calif., campus on Monday.

Jobs took a medical leave in January to deal with what he initially described as a hormonal imbalance, but which was apparently serious enough to require a liver transplant.

For nearly six months, Apple spokespeople would say only that they looked forward to their chief executive returning to Apple before the end of June.

He seems to have made it back to One Infinite Loop with more than eight days to spare.

Jobs was quoted early Monday in a press release announcing the sale of more than 1 million iPhone 3GSs. It was his first public statement since Jan. 21.

That press release also signaled a typographical change in the name of the new iPhone — from 3G S to 3GS — a small but welcome improvement in which some Apple watchers thought they saw the master micromanager’s hand.

It’s not clear yet whether Jobs’ appearance Monday was a one-time thing or if he is planning to come back to work full time.

Apple has not yet returned a request for comment or confirmation.

UPDATE:
USA Today
reports that Jobs has been in contact with Apple employees in the past few weeks via e-mail and Reuters says one of its reporters spotted Jobs leaving the campus Monday:

“[He was] dressed in his trademark black turtleneck and jeans. He walked out chatting with another person before climbing into a black car that then drove off.”