TIJUANA – Four decapitated bodies have been found since Monday in two locations in Tijuana.

Three were discovered early Tuesday in the same spot with the same message scrawled in black marker across their backs: “We are people of the weakened engineer.”

The identities of the four men, and a fifth found with his face disfigured, remained unknown late Tuesday. But the message apparently refers to Fernando Sanchez Arellano, who heads the once-powerful Arellano Felix cartel. He is nicknamed “El Ingeniero,” the engineer.

The deaths come amid a rise in violence in recent days in the city, where law enforcement officials say criminal groups are fighting for control of the region. They follow the arrest in Tijuana last week of a suspected powerful cartel leader with San Diego connections, Pedro Ignacio Zazueta Rodriguez, known as “El Pete.”

State investigators said the three bodies found Tuesday off the Via Rapida Oriente, a highway that crosses the city, belonged to men between the ages of 30 and 40. Their hands were bound, and their heads were burned and placed near the corpses on an empty, trash-filled lot.

Another decapitated victim was discovered early Monday miles away in an isolated area off of Bulevar 2000, which leads from eastern Tijuana to the coastal areas. Nearby lay the body of another victim, who was disfigured and stabbed repeatedly.

Tuesday's deaths brought the number of reported homicides in Tijuana so far this year to 320; 337 people were reported slain last year.

Baja California investigators gave no information about leads in the case. Rommel Moreno Manjarrez, the state attorney general, linked the recent rise in killings to a “settling of accounts” among criminal organizations after a series of key arrests.

On Friday, members of a federal task force arrested Zazueta, 35, at Tijuana's Caliente Racetrack. He also uses the identity Ruben Rios Estrada. U.S. law enforcement officials say he belonged to a violent Logan Heights gang known as the Red Steps.

During the 1990s, Zazueta spent time in a California prison on charges of auto theft and tampering with a weapon. He was deported twice, in 1992 and 1999, said Lauren Mack, a spokeswoman with U.S. Immigration and Customs Enforcement.

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