He said air traffic controllers immediately contacted the nearest control towers on the African mainland at Libreville, Gabon and Brazzaville, Republic of Congo, to see whether they had heard from Krause. They had not.
Navy and Coast Guard vessels are still looking for any trace of Krause's plane, Barreto said.
The family's website said they have sent a Portuguese-speaking envoy to Sao Tome, at the family's expense, to "get the official documentation as to what actually took place there from Jerry radioing in to land to their responses and follow-up.
"Their stories haven't been confirmed and haven't been consistent," the message complained.
Krause's employer, Eric van der Gragt, said the control tower did not inform others that there was a missing pilot and plane until almost 24 hours after the disappearance.
"The tower just didn't inform people that he had disappeared," van der Gragt, owner of Bamako, Mali-based Sahel Aviation Service, said in a telephone interview.
He said he sent a plane to search for Krause for two days that week, after the Sao Tome Coast Guard had found nothing on the Monday and Tuesday following his disappearance. The Sahel plane searched around the twin-island nation of Sao Tome and Principe, he said.
Van der Gragt said the turboprop Beechcraft that Krause was flying did not belong to his company but, he believed, to a company based in Senegal.
Krause's family is heartened that searchers have found nothing in the Gulf of Guinea, saying that an absence of wreckage or emergency locator transmitter signals are hopeful signs.
The oil-rich Gulf of Guinea, where Krause disappeared, has been increasingly targeted by armed pirates who hijack ships' cargoes, including a British ship in February.
At their Web site and on Facebook, the Krause family details how they lobbied officials of the French cellular service Orange, to which the pilot was subscribed, in an effort to get them to try to track his iPhone and discover his last position. At first the company resisted, then said it was unable to help because his subscription was based in Mali, according to the Web site. Orange was able to turn off the iPhone from afar, to conserve its battery.