Searchers recovered the bodies of six of the seven crewmen killed when an Argentine-flagged sand barge sank over the weekend after colliding on the Parana River with a Paraguayan-flagged tugboat, Argentine officials said.

The body of Gustavo Caracciolo, captain of the Argentine barge Rio Turbio, was found Sunday morning, coast guard Maj. Sergio Gaetan said.

Hours later, the coast guard found the bodies of first mate Ramon Rodriguez, helmsman Marcelo Cordoba, engine-room officer Felipe Aguirre, boatswain Jose de la Fuente and seaman Cristian Marmet.

The marine patrol is still looking for seaman Luciano Luna, 24, Gaetan said.

The Rio Turbio, still capsized, had sailed from the city of Ava Payagua in Buenos Aires province at kilometer 102 (mile 63) on the Parana River near the city of Zarate.

The coast guard has detained the captain, helmsman and an officer in charge of maneuvers of the Ava Payagua tug that was sailing with 12 people aboard.

On Saturday the coast guard working the area with divers managed to rescue one member of the Rio Turbio crew, who was slightly injured but has since recovered satisfactorily.

"It looks like the Paraguayan tug went out of control and crashed into the Argentine vessel, a sand barge carrying a full cargo that sank rapidly," Juan Carlos Pucci, secretary general of the river workers union, said in a statement on the radio.

"We want to lodge a complaint against all Paraguayan shipowners because, to our understanding, they are not navigating under optimum conditions," another union representative, Leonel Vazquez, said.

He said that river workers have been complaining "for some time" about the situation and added that "when there's a collision," Paraguayan ships "always have something to do with it."

According to reports, Argentine Security Minister Nilda Garre is overseeing rescue operations and aid for crew members of the capsized sand barge.