Apple's CEO and co-founder Steve Jobs reported for duty at Apple's Cupertino headquarters on Monday, according to reports.

CNBC's Jim Goldman said he met a wall of silence when asking the company's PR machine about Jobs' whereabouts, but claimed Apple employees confirmed Jobs was at work yesterday.

Meanwhile, Reuters reported that Jobs "was seen leaving the main Apple building in Cupertino and getting into a black car alone that was driven off by men in black suits with ear-pieces".

Jobs was originally scheduled to resume his CEO position at the end of June, after announcing in January that he was stepping aside for six motnhs.

Apple chief operating officer Tim Cook has been standing in for the Apple co-founder, who revealed he was suffering from a hormonal imbalance last year.

Reports last week claimed Jobs received a liver transplant about two months ago to treat an undisclosed medical condition. The Wall Street Journal first reported the story on Friday, claiming Jobs received the transplant in Tennessee. The newspaper said he was recovering well and is expected to return to work later this month on a part-time basis.