WEST, Texas - The Bureau of Alcohol, Tobacco, Firearms and Explosives said Wednesday afternoon that the 2013 fire at the West Fertilizer Company was intentionally set.
Robert Elder with the ATF said the fire was incendiary and a "criminal act."
At a Wednesday news conference, Special Agent In Charge of the Houston Field Division, Rob Elder, declined to say what substance started the fire saying he wanted to be able to verify the validity of any potential witnesses or people who come forward claiming to have information.
No one has been arrested. Channel 2 Investigates has learned that federal investigators do feel they are on the right path to identifying those responsible.
"I think we are on the right track I think that answers your question without actually answering it. I believe we are on a strong path to getting to the truth here," Elder told Channel 2.
A federal grand jury has subpoenaed people in the criminal investigation, Channel 2 Investigates has confirmed.
"We have brought witnesses before the grand jury," Elder said. "There are still more we hope to bring."
The ATF and Crime Stoppers announced a $52,000 reward for information about the fire.
The ATF has been investigating for more than three years and recently completed its final cause and origin report.
The full report will not be released because the investigation is still ongoing, Elder told Channel 2 investigative reporter Jace Larson.
The ATF met with some of the families of people who died when ammonium nitrate exploded and killed 15 people.
Ten first responders and two volunteers died while fighting the initial fire, which was reported 18 minutes before the explosion.
The explosion registered as a small earthquake, sent debris flying more than a mile away and left a 93-foot-wide crater at the site of a fertilizer storage building on the site.
Elder says the investigation will continue until there is nothing left to investigate.
"I don't like to put percentages on things because if we get the right break the percentages go up to 100 I don't get the right break they stay at 0. If we don't try we don't we never increase our percentages," he said.
If you have a tip about this story or a story idea for investigative reporter Jace Larson, email or text him at email@example.com or 832-493-3951.
Attorneys for many of the victims of the fire released a statement Wednesday that read: "There has been some misinformation about what ATF was announcing today. As McLennan County District Attorney Abel Reyna and ATF Agent in Charge Robert Elder stated, the ATF is looking at the cause and origin of the fire. The storage of the ammonium nitrate that exploded was not part of the ATF investigation. The ATF did not investigate what exploded, why it exploded or who knew that it could explode. All of that is the subject of civil litigation to be heard by a McLennan County jury."