AUSTIN (CBS 11 NEWS) – A total of 28 state and federal agencies are investigating why the West Fertilizer Company’s plant caught fire and exploded two weeks ago.

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The state fire marshal Chris Connealy, calls the probe an archeological dig. “Our goal is to have the origin and cause part of the investigation completed, and make a determination by May 10th.”

At a hearing before the Texas House of Representatives’ Homeland Security and Public Safety committee Wednesday, Connealy said they may never know what sparked the fire and blast. “If we eliminate all the causes, and we get down to two, and we can not eliminate the other one for example, it’s going to have to be ruled undetermined. Does that mean it was a poor fire investigation? Absolutely not.”

Much of their focus is on the 270 tons of the potentially explosive ammonium nitrate stored at the plant.

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State agencies testified the company did report the chemicals stored at the facility as required.

The weather’s already been dismissed as a cause, and authorities say there’s no specific evidence the incident was a crime or terrorism.

The chairman of the Texas Commission on Environmental Quality, Bryan Shaw tells me they’ve also ruled out another chemical stored at the plant that the EPA considers extremely hazardous.

Shaw says, “Initially, people were jumping to conclusions it was anhydrous ammonia, which proved not to be true and now they are speculating it was the ammonium nitrate. We need to make sure we understand what the cause was.”

The hearing also revealed there are 41 facilities across Texas storing large amounts of ammonium nitrate, including four each in Cooke and Navarro Counties, and three in Parker County.

Officials say the EPA doesn’t consider ammonium nitrate extremely hazardous.

Even so, state representative Joe Pickett, Democrat of El Paso asked the chief of the State Division of Emergency Management, Nim Kidd, to contact fire chiefs where those facilities are located.

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Kidd responded, “If you’re asking if we suggest to the fire chiefs to go in and have discussions with the facilities operators, yes, we can suggest that.”

While the state says West Fertilizer Company did report the ammount of ammonium nitrate stored there, none of the state agencies raised any red flags about how much was being stored there.

The head of the Texas Department of Health Services, David Lakey, told the panel, “It’s limited to, did you fill out the paperwork? Did you report what’s in your facility, not whether those chemicals are stored safely or not.”

But Shaw, the Texas Commission Environmental Quality chairman says it’s too early to come to conclusions. “I always like to ask what we would do differently if we could go back one day before the explosion, and at this point, we don’t know any information that tells is that that should have been a risk for an explosion occurring.”

But CBS-11 has learned the U.S. Department of Homeland Security is investigating whether the company should have notified them about the quantity of ammonium nitrate at the plant.

The state insurance commissioner, Eleanor Kitzner, says there’s no state requirement that a company must conduct evacuation training or drills. “If there’s a requirement, I’m not aware of it.”

I asked her if she was surprised by that, if that needs to change.

Kitzner said, “Well, I think we have to wait for the investigation to be concluded to see what actually caused this.”

We were unsuccessful Wednesday in contacting the owner of the plant, Donald Adair.

Kidd, the chief of the State Division of Emergency Management told lawmakers that his agency requires local governments to conduct training exercises and drills.

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One McLennan County Commissioner told me the county has done just that.