Did the ATF Destroy the Evidence at Fertilizer Plant Explosion?

If you've seen the video of the fertilizer plant explosion, you know that a strange bright light from the left approaches the plant a split second prior to the explosion. If it was a missile of some kind, chemical or physical residues of it might be left in the debris, and chemical analysis of the site might reveal it. But now the Chemical Safety Board (the agency probably most qualified to chemically analyze the site), has claimed that they have been prevented from doing their job. Further, they claim that evidence has been removed from the site, after their request to examine it:

“Access was denied at first, then it was limited thereafter, then it was denied again. Generally to get access, our investigators and experts had to be assigned to ATF work teams, where they often given shovels and rakes and assigned to labor tasks sifting debris, for whatever objects ATF was interested in. They had very little access to to the site for the purposes of the CSB investigation. From May 13 onward ATF denied us any access ‘until further notice’ and that has remained the status to the present day.

There was one block of AN that disappeared after we indicated we wanted to sample it. Additionally ATF removed the fertilizer materials that survived in the bins before we could sample any. We were not permitted to draw our own samples of the surviving material in the bins. We understand ATF conducted some form of testing, but we have not received any results.

We did obtain some samples but other chemical materials of interest were removed after we indicated we wanted to sample them.

Concerning the tour of Dr. Moure-Eraso, this occurred on the afternoon of Thursday, May 2.  It involved Dr. Moure-Eraso, Daniel Horowitz, Don Holmstrom, and some senior ATF and SFM officials.  It was essentially a ceremonial, perimeter tour of about one hour, similar to those previously provided to various elected officials and members of the news media. Dr. Moure and the various ATF/SFM personnel walked along the periphery of the site, on the railway grade (where many trains pass each day and can observe the site) and from there they briefly overlooked the crater and some other parts of the site from a distance.

This was not comparable to in-depth site access and evidence collection for our investigators and experts, which would be a multi-week or month process. From May 13 onward, all site access was denied ‘until further notice’ per the email of the ATF supervisor, and that has remained the situation since then. We are not aware of anything that precipitated this change on site access; we certainly didn’t do anything to prompt it, and the May 4 agreement specifically had specifically stated the CSB would have site access.”

UPDATE: My hypothesis that the Boston Bombing and Ricin Letters were diversions so that most people wouldn't pay much attention to the West Texas Fertilizer Plant Explosion seems to be holding up rather well. If one looks at stories in conspiracy theorists' websites, the Boston Bombing takes up the most space. It's difficult to find mention of the other two stories.