Monisha Kaltenborn has declined to confirm or deny reports that it is Marcus Ericsson's Swedish backers who have bought the Sauber team.

The Swiss outfit announced on Wednesday that it will be fully acquired by a Swiss-based group called Longbow Finance, resulting in the retirement of founder Peter Sauber.

"As a Swiss company, we are very pleased with having secured the future of a Swiss presence in a highly specialised and innovative industry," said Longbow's Pascal Picci.

Yet Swiss newspaper Blick claims that Longbow is in fact powered by Tetra Laval, a Swedish multinational headed by billionaire Hans Rausing that already finances Sauber driver Ericsson's seat.

"On the background of the purchase agreement, we do not comment," Kaltenborn, who remains team boss, told the newspaper when asked about the Tetra Pak rumours on Thursday.

She also would not say what Longbow has paid for the team, which will continue to be called Sauber.

Kaltenborn admitted: "Of course I am very relieved and happy that we found a solution. It is certainly one of the best days in my tenure as team boss.

"Now we need to stabilise as a company and then move forward step by step.

"Having a competitive car as soon as possible is one of the key strategic objectives. But giant leaps should not be expected this season. The challenges remain enormous, but now at least they are positive challenges."

Kaltenborn also would not comment on claims that, with Ericsson's backers now owning Sauber, the 25-year-old Swedish driver's career is at least secure.

"As I said, we will analyse and discuss all of this in the next weeks. We only ever do contracts for one year with drivers," she insisted.

The season continues this weekend with the Hungarian Grand Prix.