Lindsay Wilcox, NBC 5 News
West residents in Zone 2 were allowed to return home Tuesday, and some residents found their homes were beyond repair.
Officials in West released new details into the recovery and investigation Tuesday into an explosion that killed 14 and injured more than 200 last Wednesday.
On Tuesday, Assistant State Fire Marshal Kelly Kistner said the "slow and methodical" investigation continues and is "adhering to a scientific process." Kistner said officials are evaluating the devastation from the areas with least damage to most damage first while they continue to look for the heat source that led to the explosion.
Kistner also said investigators are trying to determine what material first ignited, leading to the massive explosion. Once the sources of ignition and heat are found, the fire can then be classified into one of four causes: natural (act of God), accidental, incendiary (intentional) or undetermined.
At this point, investigators do not know the cause of the explosion. But investigators have determined that a rail car full of ammonium nitrate was not the cause of the fire, Kistner said.
Kistner said officials still did not have an inventory of the chemicals that were at the facility at the time of the explosion and their quantities.
A three-dimensional rendering of the crater created Monday indicated to investigators that the crater at the site of the explosion was 93 feet wide with a depth of 10 feet, according to Robert Chapman, Bureau of Alcohol, Tobacco, Firearms and Explosives special agent in charge.
Meanwhile, McLennan County Sheriff Parnell McNamara addressed rumors of protesters attending funerals for victims, saying the following:
"We've been made aware that there could be individuals or groups who plan to picket or protest during the funeral services of our fallen heroes. Make no mistake about it, any attempt by any group or organization to disrupt the funerals of any of our victims of this tragedy will be dealt with swiftly and prosecuted to the fullest extent of the law. I've contacted District Attorney Abel Rena, and he has assured me of his cooperation in this matter. We're simply not going to tolerate that."
At a town hall meeting Tuesday night, Mayor Tommy Muska assured residents that no homes would be demolished before they could try to salvage belongings -- with the help of search-and-rescue crews.
He also said engineers would begin inspecting the underground water system Wednesday morning.
“It's a 2.4-magnitude earthquake that just hit this town, so I'm sure some of those pipes are not going to be good,” he said.
Everyone in West has been told to boil water until experts determine the water is safe to drink.
NBC 5's Scott Gordon contributed to this report.