Perhaps it was something to do with typhoons/weather conditions at the time? This is interesting.
"The
1997 Pacific typhoon season was a record-breaking season featuring 11 tropical cyclones reaching super typhoon intensity, tying the record with
1965 with the most violent tropical cyclones globally. It has no official bounds; it ran year-round in 1997".
Typhoon Peter (Daling)
Typhoon (JMA)
Category 1 typhoon (SSHWS)
Duration June 22 – June 28
Peak intensity 120 km/h (75 mph) (10-min) 970
hPa (
mbar)
From June 22–26,
PAGASA tracked the storm, and named it Daling.
[13]
Ahead of the storm, international and domestic flights were cancelled throughout Japan and ferry service was suspended. Heavy rains produced by the storm triggered landslides throughout Japan,
[17] resulting in three fatalities.
And this is a bit more info on the weather events at the time.
Monthly Weather Review