The head of the charter airline whose plane crashed in the Andes last week has been detained by Bolivian prosecutors for questioning as authorities look into whether the tragedy that killed 71 people stemmed from negligence.

Gustavo Vargas, a retired Bolivian air force general, was picked up in Santa Cruz along with a mechanic and secretary who worked for him at LaMia airline.

All are being questioned about their roles in letting a British-built short-range jet attempt a more than four-hour flight from Santa Cruz to Medellin, Colombia, for which it barely had enough fuel, in violation of aviation norms.

Prosecutors said the questioning was expected to last eight hours and afterwards they would decide whether any of the three would be formally arrested.

Earlier, authorities raided the airline's offices as well as those of the agency that oversees air traffic in Bolivia.

Authorities are also looking into whether LaMia, which received permission to fly only earlier this year, was favoured by Vargas's son, who headed the office responsible for licensing aircraft in Bolivia's civil aviation agency.

After the crash, LaMia had its licence revoked and several aviation officials, including Vargas's son, were suspended.

The plane was carrying Brazil's Chapecoense football team to the opening match in the Copa Sudamericana tournament's finals when it crashed outside Medellin on November 28.

Prosecutors from Brazil, Bolivia and Colombia are expected to meet in Santa Cruz to combine efforts in determining the causes of the crash. They also are studying how the airline, which despite a questionable history amassed an impressive list of clients from among South America's top football clubs, was allowed to operate.

One of the six survivors of the crash said he had been reassured by the airline before take-off that the plane would make a refuelling stop in the Bolivian town of Cobija, as it had on previous flights north.

"I don't know if it was a fuel problem - the investigation will determine that," Erwin Tumiri said from his modest home in Cochabamba, where he is recovering from the crash. "But every time we flew we went first to Cobija and returned the same way to refuel. On this occasion they said we'd do the same."

Meanwhile, an employee in Bolivia's aviation agency turned up on Tuesday in Brazil seeking asylum.

In a document widely circulating in Bolivian media, the worker, Celia Castedo, appears to have pointed out a number of irregularities in the aircraft's flight plan, including not having enough fuel, to LaMia's dispatcher, who was killed in the crash. The authenticity of the document could not be immediately verified.

Brazilian federal police said Ms Castedo applied for refugee status upon crossing the border by land.

In Bolivia, a senior government official said Ms Castedo, who was among officials suspended following the crash, was potentially evading justice and should be immediately deported.

"What she has done is very serious," minister Carlos Romero told reporters, denying that she faced any persecution in Bolivia. "It's a way of escaping the judicial system."

Ms Castedo's son Sebastian said that the truth would "come later by authorities other than those in Bolivia". He said he did not know where his mother was.

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