Speaking to Spanish TV station Movistar, Hasegawa said: "The first day we had an oil system issue, the oil tank. Normally the oil tank has to manage the oil level but this year we had some bad oil management so that is why we need to modify the oil tank system.
"The second day we have a mechanical issue and still we don't know the root cause of the problem. This is more fundamental and more serious I think. We need to find out what was causing the issue."
When asked if the problems could compromise Honda's start to the F1 season, Hasegawa said: "Oil tank definitely not. [The] mechanical issue, I don't know, yet to be confident about that, but of course I worry about that."