WEST, Texas (KCEN) - Texas Fire Marshals made an announcement Thursday regarding the cause of the fertilizer plant explosion in West, Texas, that killed 15 people and injured hundreds on April 17.

According the Fire Marshals, the cause of the explosion is undetermined at this time. Multiple potential causes could not be completely ruled out, so the investigation will continue.

"This community has suffered a great tragedy, and us, along with the State Fire Marshals, ATF and 28 plus agencies all work in one common goal, to understand what happened. To give closure to these families," Texas Fire Marshal Chris Connealy said. "At this time, the State Fire Marshal's Office and the ATF are ruling that the cause of the fire is undetermined."

There are multiple lawsuits against the owner of the plant, claiming negligence in policies, procedures, training, supervision, maintenance and repair.

The last time OSHA inspected the plant was in 1985. It was cited for two serious violations regarding respiratory standards and the way chemicals were handled and stored, along with four lesser violations.

Also, state records show that the plant was housing 270 tons of ammonium nitrate, a potentially explosive chemical. That amount was not reported to the Department of Homeland Security, and is more than 1,000 times the amount that triggers safety oversight by the DHS.

There is a history of tampering at the fertilizer plant. Records from the McLennan County Sheriff's Office show numerous thefts of anhydrous ammonia, a highly explosive liquid gas that can be used to make methamphetamine.

Since 2002, there have been five reports of leaks, 11 reports of thefts and robberies, seven calls for suspicious cars and people and one trespass.