Ueberlingen, Germany ? A collision-warning system was out of service and an air traffic controller was on a break when a Russian jetliner slammed into a cargo plane high above Germany, officials said Wednesday adding to questions surrounding the crash that killed 71 people.

As an international investigation began, officials at Swiss air traffic control disagreed on whether the controller who took a break while the warning system was down had violated rules and details emerged of a report that said Swiss aviation radar was below European standards.

Criticism focused on Swiss controllers in charge of the southern German skies where the two planes collided late Monday, raining wreckage and bodies over a pastoral area of rolling fields and forests across Lake Constance from Switzerland.

The Swiss insist the 50-second warning they gave the Russian pilot was enough time for him to drop the Tu-154 he was flying for Bashkirian Airlines out of the way of the Boeing 757 cargo jet. But German officials said that was far less than usual, and Russian officials also blamed the controllers.

German prosecutors in the city of Konstanz opened a criminal investigation into the collision Wednesday, saying they also expect to question Swiss flight controllers.

Patrick Herr, a spokesman for Swiss air traffic control, said it was “a purely theoretical question” whether the Zurich tower’s warning system alone could have prevented the disaster. “Many signs point to an exceptionally unlucky combination of circumstances.”

Maintenance on the warning system typically is done during periods of light air traffic. Monday’s collision happened shortly before midnight.

Adding to the confusion, officials at Skyguide, the private company that provides Swiss air traffic control, gave conflicting accounts on whether the controller’s break at the time of the crash was allowed.

Anton Maag, chief of the Zurich airport control tower, said Skyguide rules forbade leaving a lone controller on duty without the aid of the warning system. But one of his aides, Philipp Seiler, later told The Associated Press that this rule did not apply at night.

Meanwhile, details emerged of an official report that said Skyguide’s radar system fell below European safety standards. The report by the Swiss Aircraft Accident Investigation Bureau, completed last month and published on the Internet, examined three near misses in Swiss airspace between 1998 and 2000.

It said big differences between radar readings issued by Geneva and Zurich centers called the system’s reliability into question. It also said differences between the way radar data was handled by Skyguide compared to neighboring countries could lead to misreadings of planes’ locations on radar screens by up to 1,600 feet.

The recovered flight data recorders of both planes were brought to a German federal lab Wednesday for decoding. But the head of the lab, Peter Schlegel, already voiced suspicions about the 50-second warning.

“It seems to have come a bit late, though I don’t want to pass judgment right now,” he said on ARD television.

Salvage crews had recovered 38 bodies by Wednesday evening and autopsied 24, police said. However, only the two pilots of the cargo plane flying for DHL International had been identified.

Officials believe as many as 20 more bodies of passengers and crew may be in the fuselage, still strapped into their seats.

German forensic experts trying to identify the victims prepared for the arrival of families of the Russian children, expected today at the scene.

“We must make it clear that the identification will be difficult and at this point we are not sure that we will be able to identify all the victims,” said Thomas Schaeuble, the state interior minister of Baden-Wuerttemberg.

Schaeuble said a list would be prepared for relatives of items that they should bring to make the identification easier such as pictures, details of what clothes the victims were wearing and medical or dental records.