A Mexican soldier watches a key intersection that leads directly to the U.S. outside the Mexican city of Reynosa in 2010. (Don Bartletti / Los Angeles Times)

MEXICO CITY -- Five high school students waiting for a bus were killed Wednesday when a pickup truck being chased by Mexican army forces careened out of control and plowed into them in the violent northern border city of Reynosa, authorities said.

The pickup's occupants, thought to be likely drug cartel henchmen, escaped, authorities said. The youths ranged in age from 13 to 15. A woman and a 5-year-old girl, waiting in cars nearby, were injured.

Hours after the incident, dozens of parents and teachers from local schools blocked a main Reynosa highway to protest.

Also Wednesday, five people were killed in a shootout between security forces and gunmen in the resort city of Puerto Penasco, often called Rocky Point in the U.S., in western Sonora state, officials said. Tatiana Gomez, spokeswoman for the Sonora state attorney’s office, said the five who died were suspected criminals.

The regional newspaper Riodoce reported that one of the dead was Gonzalo Inzunza, head of the Sinaloa cartel’s operations in Sonora and Baja California. If confirmed, it would be a rare blow to the powerful drug-trafficking network led by fugitive billionaire Joaquin “Chapo” Guzman.

Two years ago, the U.S. government placed Inzunza on its so-called kingpin blacklist, seizing his U.S.-based assets and forbidding American firms and individuals to do business with him.

The shooting took place on Sandy Beach, a spot about 50 miles from Mexico’s border with Arizona and a popular tourist destination for Americans. Gomez denied earlier reports that hostages had been taken during the firefight and said authorities “restored calm.” The U.S. Consulate in Nogales issued an emergency warning for its citizens in the area to “maintain a high level of vigilance.”

In the Reynosa deaths, the attorney general for Tamaulipas state, where the city is located, identified the people in the fleeing vehicle as “armed civilians” -- code for gangsters in parts of Mexico where authorities and press have been intimidated, or bought off, by the cartels and have decided to use euphemisms.

Tamaulipas is especially dominated by brutal cartels, including the Zetas paramilitary force and remnants of the Gulf cartel allied, at least temporarily, with the Sinaloa organization. Information on frequent gun battles is publicized on only the most minimal level.

The Mexican press has reported several recent incidents in which military pursuits of suspects have gone wrong, resulting in fatal crashes and even the killing of kidnap victims that the army was trying to rescue.

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wilkinson@latimes.com

News assistant Cecilia Sanchez of The Times' Mexico City bureau contributed to this report.