Reports from the scene mention the damage:
Captain Chris Boyle
Engine 94 - 18 years
Boyle: ... on the north
and east side of 7 it didn't look like there was any damage at all,
but then you looked on the south side of 7 there had to be a hole
20 stories tall in the building, with fire on several floors. Debris
was falling down on the building and it didn't look good.
... Then we received an order from Fellini, we're going to make a move on 7. That was the first time really my stomach tightened up because the building didn't look good. I was figuring probably the standpipe systems were shot. There was no hydrant pressure. I wasn't really keen on the idea. Then this other officer I'm standing next to said, that building doesn't look straight. So I'm standing there. I'm looking at the building. It didn't look right, but, well, we'll go in, we'll see.
So we gathered up rollups and most of us had masks at that time. We headed toward 7. And just around we were about a hundred yards away and Butch Brandies came running up. He said forget it, nobody's going into 7, there's creaking, there are noises coming out of there, so we just stopped. And probably about 10 minutes after that, Visconti, he was on West Street, and I guess he had another report of further damage either in some basements and things like that, so Visconti said nobody goes into 7, so that was the final thing and that was abandoned.
Firehouse: When you looked
at the south side, how close were you to the base of that side?
Boyle: I was standing
right next to the building, probably right next to it.
Firehouse: When you had
fire on the 20 floors, was it in one window or many?
Boyle: There was a
huge gaping hole and it was scattered throughout there. It was a huge
hole. I would say it was probably about a third of it, right in the
middle of it. And so after Visconti came down and said nobody goes
in 7, we said all right, we'll head back to the command post. We lost
touch with him. I never saw him again that day.
http://www.firehouse.com/terrorist/911/magazine/gz/boyle.html
Fire chief Daniel Nigro clearly thought the building
could collapse. Here's why:
The biggest decision we had to make was to clear the area and create
a collapse zone around the severely damaged [WTC Building 7].
A number of fire officers and companies assessed the damage to the
building. The appraisals indicated that the
building's integrity was in serious doubt.
http://www.cooperativeresearch.org/entity.jsp?id=1521846767-634
Another fireman reported damage that progressed as the day wore on.
Deputy Chief Peter Hayden
Division 1 - 33 years
Hayden:...also
we were pretty sure that 7 World Trade Center would collapse.
Early on, we saw a bulge in the southwest corner between floors 10
and 13, and we had put a transit on that and we were pretty sure
she was going to collapse. You actually could see there was a visible
bulge, it ran up about three floors. It came down about 5 o'clock
in the afternoon, but by about 2 o'clock in the afternoon we realized
this thing was going to collapse.
Firehouse: Was there heavy
fire in there right away?
Hayden: No, not right
away, and that's probably why it stood for so long because it took a
while for that fire to develop. It was a heavy body of fire in there
and then we didn't make any attempt to fight it. That was just one of
those wars we were just going to lose. We were
concerned about the collapse of a 47-story building there.
We were worried about additional collapse there of what was remaining
standing of the towers and the Marriott, so we started pulling the
people back after a couple of hours of surface removal and searches
along the surface of the debris. We started to pull guys back
because we were concerned for their safety.
Firehouse: Chief Nigro said they made a collapse zone and wanted everybody away from number 7 - did you have to get all of those people out?
Hayden: Yeah, we had to pull everybody back. It was very difficult. We had to be very forceful in getting the guys out. They didn't want to come out. There were guys going into areas that I wasn't even really comfortable with, because of the possibility of secondary collapses. We didn't know how stable any of this area was. We pulled everybody back probably by 3 or 3:30 in the afternoon. We said, this building is going to come down, get back. It came down about 5 o'clock or so, but we had everybody backed away by then.
http://www.firehouse.com/terrorist/911/magazine/gz/hayden.html