Listen to the sentence and concentrate on the words in red.
Sarah Montague (credit: BBC)
If you are an EFL learner, you might want to make a recording of your own version of this sentence. Then compare it with Ms Montague's and concentrate on the vowels in these three words. Does she pronounce fire as /aɪə/ or /aə/ or /a:/? What about the other two words? Do YOU pronounce them with a diphthong plus schwa or even with a monophthong? Try to imitate the way she pronounces them. Needless to say that you do not have to pronounce these and similar words like that, but it's a nice exercise.
Besides: Can you pronounce the initial phrase "[i]bvestigators are trying to find out" at a similar speed? Try this as well.
1My thanks go to Paul Carley