The decapitated bodies of 25 men and two women have been found near Guatemala's border with Mexico.
The bodies were discovered at a ranch in Peten province, 500km (310 miles) north of the capital.
The chief of police said the killings were probably linked to a battle between rival drug gangs fighting for control of the area.
Northern Guatemala is an important transit point for drugs smuggled from South America to the United States.
Army spokesman Col Ron Urizar said dozens of soldiers had been sent to the Mexican border to prevent any suspects from fleeing the country, El Pais reported.
He said ground and aerial surveillance was being carried out in co-ordination with the Mexican authorities.
Officials said the victims appeared to have been ambushed by gunmen.
They are investigating whether the deaths were related to the Zetas drug gang, which has been expanding its operations into Guatemala from Mexico.
Guatemalan law enforcement officials say the gang has increasingly moved its operations south since Mexican President Felipe Calderon stepped up his country's fight against the drugs trade.
In February, the Guatemalan government lifted a two-month siege of the Alta Verapaz province - just south of Peten - in an attempt to combat the Zetas.