A similar bomb was found and deactivated outside the entrance of a nearby bank, state Attorney General Evencio Martinez told national radio station W Radio.
"I believe it could be (the work of) local groups, given the type and style of device," Martinez said.
He denied the bombs were related to the People's Revolutionary Army, a small leftist group that bombed gas pipelines in July. Sears in Mexico is operated by Mexican billionaire Carlos Slim. In 2004, a faction of the rebel group placed small bombs outside banks and an office of Telmex, Slim's telephone company.
Television footage from the shopping mall, where the bomb exploded hours before businesses opened, showed glass scattered across a parking lot and damage to a steel security curtain and parts of the entrance.
Oaxaca's state government said in a news release that police were investigating.
Oaxaca has suffered more than a year of political unrest, and on Tuesday, Amnesty International Secretary General Irene Khan urged Mexican federal officials to investigate alleged police abuse against demonstrators.
Khan presented a report describing the unsolved killings of 18 people, arbitrary detentions and other abuses during last year's Oaxaca protests.
"The federal government cannot avoid its responsibility to guarantee the protection of human rights in the state of Oaxaca," Khan said.
The conflict began in May 2006 as a strike by teachers seeking higher pay and quickly grew into a broader movement known as the People's Assembly of Oaxaca, or APPO. It included Indian groups, students, farmers and leftists who claim Gov. Ulises Ruiz rigged his electoral victory and has repressed opponents.
Ruiz, who met with Khan on Tuesday, rejected the report.
"We told them that we believe those who wrote it are advisers for the APPO," Ruiz said after the meeting.
Güncelleme Tarihi: 02 Ağustos 2007, 12:19