Suu Kyi, who has spent about 10 of the last 17 years in home detention, was most recently taken into custody on May 30, 2003, after her motorcade was attacked by a pro-junta mob as she was making a political tour of northern Myanmar.
That detention order expired early Saturday, and her supporters were hoping the military government would grant her freedom.
But the government official said Saturday morning that her detention order had been extended, though it wasn't immediately clear for how long. The official spoke on condition of anonymity because he wasn't authorized to discuss the case with the media.
Hours earlier, authorities beefed up security near her lakeside residence and extended barbed wire barricades on her street early Saturday. Her street was closed to traffic and more than 20 riot police with batons were deployed near the roadblocks.
U.N. Secretary-General Kofi Annan appealed to the ruling junta's chief "to do the right thing."
Police went to the 1991 Nobel Peace Prize winner's home Friday evening but there was no indication of the reason for the visit.