  The observations of supernova 1987A in underground detectors are revisited.
It is shown that, while the LSD detector in the Mont Blanc Laboratory observed
only one burst at 2h 52min 36.8sec U.T., the Kamiokande data show a possible
second burst, in addition to the well known one at 7h 35min 33.7sec U.T. This
second burst consists of a cluster of seven pulses, well above the energy
threshold of the detector, observed during 6.2 seconds starting at 7h 54min
22.2sec U.T. Do these observations imply a long duration of the collapse?
