Three years after a fertilizer plant fire in West Texas triggered a deadly explosion and nearly leveled the small town, federal fire investigators say someone intentionally set that fire. Our John Salazar is in West, where investigators laid out the surprising facts.

WEST, Texas -- Federal agents announced what they are calling a final ruling as to the cause of the fire. Saying the April 17 2013 fire was arson.

ATF Agent-in-Charge Rob Elder laid out the near-conclusion of a 37-month investigation federal government.

"The fire has been ruled as incendiary. This means this fire was a criminal act," said Elder.

The feds say the information released Wednesday is the "final ruling as to the cause of the fire."

They won't say if they have a suspect or suspects.

"What I can tell you is that while there have not been any arrests made, the 400 plus interview that has been conducted to date, has produced many leads," said Elder.

Investigators did stop their examination of former West Paramedic Bryce Reed, who was sentenced to 21 months in federal prison for possession of a bomb, months after the investigation began.

"We do not consider him a suspect in this case," said Elder.

Also ruled out are all accidental or natural causes to the fire.

"That includes smoking, spontaneous ignition, product storage, electrical, golf cart and many others," said Elder.

The ATF says it is limited in what it can say about how the fire started, yet sound confident they will solve the case.

The Texas Fire Marshal's Office -- who assisted in the investigation -- would not comment, and lawsuits filed a plant operators are still tied up in court.

ATF investigators say the West explosion is one of the most comprehensive in the bureau's history.

The federal government estimates it has spent $2 million reviewing the case. 

-- Statement from the attorney representing the victims: --

“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.”

The April 17, 2013 industrial accident killed 12 first responders, three West citizens and injured 260 others. More than 150 structures were destroyed including the West High School, intermediate school, a nursing home and an apartment complex. A middle school 2,000 feet away suffered damage but spared demolition.

--Statement from Texas Attorney General Ken Paxton:--

“The devastating explosion in West impacted all Texans, especially "those who lost loved ones that day, and forever changed that tightly-"knit community. I applaud the diligence of the federal, state, and local "agencies who are working tirelessly on this case and will assist in any "way to ensure that the perpetrators responsible for this devastating act "are found and brought to justice.”

Prior to Wednesday, the latest report on the incident came from the U.S. Chemical Safety and Hazard Investigation Board (CSB) calling the West explosion, “One of the most destructive incidents ever investigated.” 

The federal agency released their final conclusion in January earlier this year. To date, law enforcement agencies who have examined the fire and ensuing explosion have not issued an actual cause.

It has been widely reported fire investigators narrowed down three possible scenarios; bad electrical wiring, a fault electrical golf cart, or arson.

Total damage from the blast cost the community around $230 million.