Sao Paulo - A homemade bomb exploded on a street crowded with Christmas shoppers in Brazil's largest city on Friday, injuring 12 people, authorities said.

One woman remained hospitalised in serious condition after the afternoon explosion in downtown Sao Paulo, police officer Luis Fernando Weffort said. The other victims did not suffer life-threatening injuries.

Police were still investigating, but the bomb was likely left in a trash can on "25 de Marco" street, a popular shopping venue that receives nearly 500 000 people a day during the Christmas season.

No suspects had been arrested by Friday night, said Juliana

suspects had been arrested

Xavier, a spokesperson with Sao Paulo's Public Safety Secretariat.

Witnesses said the bomb might have been thrown by an illegal street vendor at a group of police officers who were patrolling the area, Veja news magazine, Brazil's largest, said on its Web site.

Other local media said a pregnant woman and a 5-year-old girl were among those injured, but police could not confirm the reports. - Sapa-AP