At least one federal official acknowledged the government had not gained complete control of the capital city of 275,000, which has been under siege for five months by striking teachers and leftist anarchists demanding the resignation of Gov. Ulises Ruiz.

In a sign that tensions had diminished somewhat Tuesday morning, columns of federal police in riot gear began allowing residents and business owners to pass through the city's central square, or Zócalo, which had been the protesters' center of operations since May.

A smattering of people could be seen Tuesday buying newspapers and crossing the square on their way to work, as police officers continued cleaning up rubbish in the area.

``We feel happy, protected and without fear,'' said Jesús Velázquez Hernández, a 20-year-old student who strolled across the Zócalo with his girlfriend. ``It's been about three months since we've come . . . because of the fear that they were going to rob me.''

But access to the Zócalo appeared to be a minor victory at best; schools and most businesses in the capital remained closed, and residents looked on in dismay as small bands of protesters used debris, stones and sand bags to re-barricade streets that police had recently cleared just two blocks from the main square.

Despite President Vicente Fox's insistence Monday that ``social order and peace has been restored'' to the capital, at least one federal official acknowledged that had not yet happened.

``I don't think so,'' Deputy Interior Secretary Arturo Chávez told the Televisa television network Tuesday morning. ``We are moving in stages. We are working toward order.''

A group of demonstrators Tuesday hijacked a small bulldozer, doused it with gasoline and set it on fire, then hurled large rocks at a column of police officers who broke away from the Zócalo a couple of blocks away to extinguish the fire.

Others climbed onto rooftops to monitor police movements, or maintained a blockade of the main highway connecting Mexico City and Oaxaca. The actions came a day after the protesters transferred their operations base to a plaza about five blocks from the Zócalo.

The demonstrators also maintained control over Oaxaca University, including its radio station, which they have used to distribute their messages. Despite rumors to the contrary, Mexican Public Safety Secretary Eduardo Medina told foreign journalists Tuesday the government had no plans to try to take back the university.

An estimated several thousand residents fed up with the violence, nearly all dressed in white as a symbol of peace, marched in support of Ruiz in a park just blocks from the Zócalo, as protesters jeered ``Rats! Sheep!''

``Long live Ulises Ruiz!'' some of the marchers chanted, while others yelled, ``Thanks PFP!'' the Spanish initials for the Federal Preventive Police. ``Ulises is staying.''

Homemaker María Elena Zarate, en route to the pro-Ruiz march, wept as protesters threw rocks at the police. ``Thank you, sirs, and may God bless you,'' she said to the officers. ``We are going to support these people who risk their lives to protect us.''

The protesters say they will not back down until they have achieved the resignation of Ruiz, whom they accuse of oppressing dissent and rigging his 2004 election.

Monday, the U.S. Embassy released a statement advising Americans against all travel to Oaxaca, one of Mexico's top tourist destinations, ``due to this increase in violence.''

Eight people have died in clashes since protesters took over the city.