CIUDAD JUAREZ, Mexico (AFP) - The United States is helping Mexican police track down two suspects responsible for killing 10 people who were celebrating a baseball victory near the border, Mexican officials said.

Two gunmen armed with assault rifles opened fire on a group of 30 people in a house near the amateur baseball field on the outskirts of Ciudad Juarez late Sunday, killing four minors and six adults, authorities said.

"We have the collaboration of US authorities to find the whereabouts of those responsible for the Loma Blanca massacre," Chihuahua state Governor Cesar Duarte said during a visit in Ciudad Juarez, which borders Texas.

The victims included a six-year-old girl.

The shooting took place in Loma Blanca, a district where federal police killed a Sinaloa drug cartel capo, Gabino Salas Valenciano, in August.

The state prosecutor's office said "one of the lines of investigation on the 10 deaths is the rivalry between organised crime groups in the area."

A Chihuahua state prosecutor, Mr Jorge Gonzalez Nicolas, said one of the victims appeared to have been a target of the suspects, who are believed to be 20 and 25 years old.

He also said five of the baseball players have gone missing and three of them may have taken refuge with relatives in El Paso, the Texan city on the US side of the border.

Ciudad Juarez was once considered the world's murder capital, with more than 3,000 people killed in 2010 alone amid a turf war between the Juarez and Sinaloa cartels, but the homicide rate has been falling in the past three years.

Survivors of Sunday's massacre said one of the gunmen shouted that they were members of La Linea, the armed wing of the Juarez cartel, and warned that they had regained control of the area.

Some officials say the murder rate has dropped in Ciudad Juarez because the Sinaloa cartel won the turf war, but local authorities attribute the drop to better police work.