A small homemade bomb exploded at a showroom of US automaker General Motors today without causing injuries, while a second device planted at a McDonalds' restaurant smoldered but did not detonate, authorities said.
The bomb exploded at a Chevrolet showroom, operated by General Motors, near Mexico City's airport, shattering windows and collapsing part of a ceiling, Mexico City Attorney General Mr Bernardo Batiz told reporters.
The second device was found at an outlet of US fast food chain McDonalds in front of the Chevrolet showroom. The device gave off smoke and a foul odor, Mr Batiz said.
The explosion came as world trade officials were gathered in Mexico City in a bid to resolve disagreements that could block the launch of new world trade talks later this year.
The blast also occurred just hours before President Vicente Fox was scheduled to give his first state of the union address.
Police said no one had claimed responsibility for the attacks, but radio reports said a guerrilla group calling itself the Group of Guerrilla Combatants of Jose Martia Morelos y Pavo was responsible. The group has never appeared publicly in Mexico.
Mr Batiz said police were beefing up patrols near Congress, where Fox was scheduled to give his address, and at restaurants, banks and businesses, which could be targets for guerrilla groups.
Today's explosion follows a string of other small bomb blasts at branches of Banamex, a Mexican bank recently acquired by US financial giant Citigroup for 12.5 billion.
The bombs caused slight damage but no injuries.