Here we go again. From the editor:

So how did the BBC report that Building 7 at the World Trade Centre had collapsed around half an hour before it did so? My earlier posting on the subject has attracted a lot of interest so we've been doing more investigating within the BBC to put together the sequence of events.

Five and a half years have passed so it's quite difficult to answer every outstanding question. But we do know quite a bit more than we did on Tuesday, as a result of checking the BBC archives and what other media were doing at the time. I've also read through some of the reports published after 9/11 to help put together the sequence of events.

Back to 11 September itself. The Twin Towers had collapsed. Other buildings were known to be damaged. Building 7 was on fire. But this was also a very confusing picture - remember we had started the day with reports that a light aircraft had struck the first tower, and at one stage there was talk of ten hijacked jets in the air. It's in the nature of rolling news that events unfold in front of you and confusion turns to clarity. It's important to remember that context when looking more closely at what happened between about 4.10pm (EDT) and 5.20pm when Building 7 finally collapsed.

CNN's chronology of events published at the time confirms they reported the building on fire and a clip from a CNN bulletin, widely available on the web, hears from a reporter at about 4.15pm EDT, 9.15pm in the UK, who says: "We're getting information that one of the other buildings... Building 7... is on fire and has either collapsed or is collapsing... now we're told there is a fire there and that the building may collapse as well."

Other American networks were broadcasting similar reports at this time and the reports from FEMA and NIST both make it clear the building was on fire during the course of the day.

One senior fire officer was quoted in a subsequent interview as saying there was a "bulge" in the building and he was "pretty sure it was going to collapse". During this time, our staff were talking directly to the emergency services and monitoring local and national media... and there was a fairly consistent picture being painted of Building 7 in danger of collapse. Producers in London would have been monitoring the news agency wires - the Associated Press, Reuters, etc - and although we don't routinely keep an archive of agency reports, we're sure they would have been reporting the same as the local media.

At 4.27pm, a BBC reporter, Greg Barrow, who is in New York, appears on our radio news channel, BBC Radio Five Live, and says: "We are hearing reports from local media that another building may have caught light and is in danger of collapse." He then responds to a follow-up question by saying "I'm not sure if it has yet collapsed but the report we have is talking about Building 7."

At 4.53pm, on the same radio station, the programme's presenter, Fi Glover says "25 minutes ago we had reports from Greg Barrow that another large building has collapsed just over an hour ago."

At 4.54pm, the BBC's domestic television news channel, BBC News 24, reports the same thing. Presenter Gavin Esler says: "We're now being told that yet another enormous building has collapsed... it is the 47-storey Salomon Brothers building."

And then at 4.57pm on BBC World (according to the clips available on the web) presenter Phil Hayton says: "We've got some news just coming in actually that the Salomon brothers building in NY right in the heart of Manhattan has also collapsed."

Because three BBC channels were saying this in quick succession, I am inclined to believe that one or more of the news agencies was reporting this, or at least reporting someone saying this.

At 5pm, News 24 repeated the news in its top-of-the-hour headlines sequence and then at about 5.10pm (again according to the clips on the web), Phil Hayton on BBC World says "More on the latest building collapse in NY - you might have heard I was talking a few moments ago about the Salomon building collapsing and indeed it has... it seems this wasn't the result of a new attack but because the building had been weakened during this morning's attack."

Some of the respondents to my earlier blog have suggested this must mean he had inside knowledge - that not only did he know the building had collapsed, he knew why.

Well in one sense that's true - for about an hour, it had been reported that the building was on fire and in danger of collapse. But he did qualify it by saying "it seems" and once again I think there's a danger of reading too much into what I believe was a presenter merely summarising what everyone had been saying during the previous hour.

Of course, with hindsight we now know that our live shot showed the building still standing in the background. But again I point to that confusing and chaotic situation on the ground - the CNN reporter who had talked about the building "either collapsed or is collapsing" also had it clearly in shot behind him, but he acknowledged he couldn't see very clearly from where he was standing. As we know, the building did collapse at 5.20pm, with the first pictures of that being broadcast on News 24 at about 5.35pm.

So that's what we know we reported. To me it paints a consistent (and reasonably conclusive) picture.

I should also mention the missing tapes. As you'll see from the details above, the absence of the BBC World tapes hasn't made much difference to our ability to look back at what happened. We have all the tapes of other BBC channels (and I now know that quite a few of you have your own copies of BBC World, which is an interesting discovery... ).

Some of you find it hard to believe we didn't keep the BBC World tapes... but we had several streams of news output running simultaneously on the day, both on radio and television as well as online and we have kept all the tapes from BBC News 24 and Radio Five Live, as well as all the BBC One bulletins. Obviously I wish we'd kept hold of the World tapes alongside all the others, but we didn't... and I don't know whether they were destroyed or mislaid. But as a result of this week's events, I have asked our archivists to get hold of copies of our original material from the organisations which do have them.

And just to be clear, the BBC policy is to keep every minute of news channel output for 90 days (in line with the Broadcasting Act in the UK). After that we are obliged to keep a representative sample - and we interpret that to mean roughly one third of all our output. We also keep a large amount of individual items (such as packaged reports or "rushes" - ie original unedited material), which we use for operational reasons - such as when we come to broadcast fresh stories on the subject. We do not lack a historical record of the event.

I've spent most of the week investigating this issue, but this is where we have to end the story. I know there are many out there who won't believe our version of events, or will raise further questions. But there was no conspiracy in the BBC's reporting of the events. Nobody told us what to say. There's no conspiracy involving missing tapes. There's no story here.