The 26-year-old German was given a 'new' chassis for last weekend's Spanish Grand Prix in Barcelona and charged to fourth despite starting 15th following a five-place penalty for a gearbox change.
Media reports in Germany suggested the previous chassis, while supposedly no different to the replacement that was used in pre-season testing, was crooked but the team said there was no evidence of that.
"The 'old' chassis has not been found to be distorted," chief engineer Paul Monaghan said in response to a query.
"The investigation is ongoing as the extent of the checks is vast in order to be thorough. No one error can be considered an entire explanation and requires further work to that completed prior to and within the Spanish GP.
"Changes to some ancillary equipment and preparation procedures has resulted from the checks made thus far," Monaghan added.
"Once all the information is available, Red Bull will address the points found in order to implement a complete solution."
Vettel, winner of the last four championships and the final nine races of 2013, has been fighting more for points than podiums so far this year.
The German complained of a lack of 'feel' from the car as Formula One entered a new V6 turbo hybrid era after ditching the old V8 engines.
Red Bull's engine partners Renault have also been playing catch-up with a power unit that has been less competitive than the dominant Mercedes one.
However, Vettel has also been outperformed by his new Australian team mate Daniel Ricciardo, who started and finished third in Spain and was disqualified from second in Australia.
Team principal Christian Horner said after Sunday's race that it looked like the Vettel of old was returning, however.
"(In 2013) his confidence was high, he was on the crest of a wave, and then you can walk on water. He had the feeling from the car everything was going for him," the Briton told reporters.
"That's what he has been searching for with RB10, and this weekend you could see in the race the recovery drive that he had, the fastest lap, he hunted down the Ferraris. It looked like he had got his mojo back."
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