A wave of bus attacks in Guatemala left 139 dead in the first half of the year, including 78 drivers who refused to pay protection money, according to an official report leaked on Tuesday.
Those killed included 33 passengers, 16 conductors and 12 suspected criminals. One-hundred-five people were also injured, according to the report from the attorney general's office for human rights, published in local media.
In the latest attacks, two drivers and one conductor died on Sunday in southern Guatemala, and gang members threw a grenade onto a bus carrying 11 security guards and a conductor in the capital late on Saturday, injuring all of them.
Interior Minister Raul Velasquez said a group of investigators would study the growing wave of attacks.
Gang members typically seek around $70 per week in protection money from bus owners to allow them to drive around the capital, where some 3,000 buses operate.
Attacks have extended across the notoriously violent Central American nation in recent months.