Bombardiers CSeries taxies on the runway just before dawn. (Photo: Bombardier)

MonTREAL — Bombardier Inc. says it believes the engine failure of one of its CSeries test planes last week occurred in the aircrafts low-pressure turbine.

The aerospace giant says a preliminary investigation also shows that the engine was known to have problems and that it had considered returning it to manufacturer Pratt & Whitney prior to the malfunction on May 29.

It also said the engine failure was not caused by the gearbox, suggesting that it was due to a manufacturing defect, rather than a design flaw.

The company confirmed Friday the details revealed in a research note with financial services firm, UBS, which it said met with Bombardier CEO Pierre Beaudoin on Thursday.

The chief financial officer of Pratt & Whitneys parent company, United Technologies, made similar comments on Thursday at an investors conference in Chicago.

Montreal-based Bombardier says it hopes to resume testing of its CSeries jets in the next few weeks, after the engine trouble stopped flight testing of four aircraft. In the meantime, three of the jets are doing ground testing.

The aircraft have flown nearly 330 hours of testing, well short of the 2,400 required to receive Transport Canada certification.

The company expects to get some credit for ground testing and anticipates flight hours will pick up as the seven test airplanes, each with different missions, take to the air.