You may say they have not found any evidence which points to terrorism, but what evidence points to a bird in the engine? Did they find some feathers?
Possibly, they publically commented on the non-criminal aspects of their investigation -- e.g. they looked for feathers in the engine, they don't find feathers in the engine, they annouce that they looked for feathers in the engine and did not find it.
The criminal part of an investigation is usually handled publically differently -- e.g. they looked for explosive chemicals in the tail section, they found no explosive chemicals in the tail section, they simply comment -- when asked -- that we have no evidence that a cime(terrorist act) has been commited at this time. Not until evidence of a real crime has been found, would they probably say so.
This is probably what has happened, however always be suspicious.