“Within 3 minutes from the time of the alarm...”

So the question is, when was the alarm issued? I was once was aboard a UA 747 that made an emergency return and landing at SFO due to one of the engines having a problem. The ARFF (fire engines) were awaiting us on the side of the runway as we were landing and chased us for a little bit as far as I could see. Of course, it was otherwise a very uneventful landing for us passengers.

In this case, did the aircraft return without anyone expecting an emergency landing, I.e., did the three minutes start when the fireball was seen by someone in the tower? Should there have been firefighting resources close by? Or perhaps they were? I think we will learn more about this over time.

Disclaimer: armchair airport traffic controller, pilot, firefighter, ...