What caused the extensive damage to Subway at WTC?

A video talks about the CBS 60 Minutes Report by Dan Rather
"Down under WTC"

They say it shows several hundred yards of blown up subway cars and extensive damage to the subway area(north of WTC1) before WTC1 fell.

What could have caused this damage if not explosions?

Does anyone have a URL for the 60 Minutes Report. The one the video cites no longer works.

The Henrik Melvang Video also says that there was a stopped clock at 10:05 that led to the FBI stating that the time of the south tower collapsing was 10:50 since this damage must have been done with WTC2 fell.
But this subway area was under WTC6 which was north of WTC1
and Melvang says WTC2 falling could not do the damage to the subway this far away and on the other side of WTC1. He also says there is evidence that WTC2 fell at 9:50; not 10:05 (media report from video with timer device)
Anyone know of evidence that WTC2 fell at 10:05? rather than 9:50?

The Melvang video also apparently shows the CNN video that shows the explosive cloud at WTC6 before the south tower falls.
Its a 4 hour video and I haven' seen all of it yet; Its also in Danish which makes the viewing slower though he has some translated on paper.

He gave a URL where he got the video sequence(CNN) but that URL no longer works.

Time of collapse, WTC2. Look at the bottom :

http://terrorize.dk/911/watches/

Looks like around ten.

from the other two clocks; and WTC2 collapse somehow caused the subway damage at WTC6 and stopped clock?