GUATEMALA CITY - An explosion ripped through a passenger bus on the outskirts of the Guatemalan capital Sunday, killing one person and seriously wounding 17 more, authorities said.

Firefighters' spokesman Mario Utum confirmed that one person died and said emergency workers have tended to victims with second- and third-degree burns.

Interior Minister Francisco Rivas said the blast is being investigated as an attack and the incident appears similar to a 2010 gang assault on a bus that left nine dead, but there was no immediate indication of possible suspects or motive.

Bus companies and taxi drivers are often extorted by gangs in Guatemala and risk being attacked if they don't pay up. Rivas said the owners of the bus had not reported receiving threats, however.

The vehicle was carrying dozens of people between San Jose Pinula and Palencia, just to the east of Guatemala City, at the time of the explosion.

Photographs distributed by emergency agencies showed people with burns covering nearly their entire bodies and the bus with a gaping hole at the back end.