Between December 9 and December 21, we'll be counting down the 13 biggest stories on throughout 2013. From pig problems (see below), to Tesla's on fire, and being held captive in China, we'll be looking into just why these stories resonated with readers here and elsewhere. For the full list, updated daily at 1:00pm EST until the 21st, visit the Top 13 In 2013 page.

On April 17, a fertilizer plant owned by West Fertilizer Company, in the Texas town of West, caught fire. As firefighters battled the blaze, of which the cause is still not known, the plant exploded, leaving six or seven firefighters, and at least two EMS responders, unaccounted for or missing and assumed dead. The blast shattered windows around the small town and left many worried that, given the plant’s proximity to a local school and residencies, that many in the surrounding area might have been injured or killed. News about the blast spread across social media, with video of the blast reaching YouTube almost immediately.

Warning: the following video is loud, so turn down your speakers or headphones.

As more first responders picked through the rubble, Donald Adair, a longtime resident of West and the owner of Adair Grain Inc., parent company to that which owned the facility, issued a statement regarding the incident, in which he said: “This has been a terrible week for everyone in West, Texas and I want to take this opportunity to express my heartfelt sympathy for those affected and my appreciation for those who responded. As a lifelong resident, my heart is broken with grief for the tragic losses to so many families in our community. I know that everyone has been deeply affected by this incident. Loved ones have been injured or killed. Homes have been damaged or destroyed. Our hearts go out to everyone who has suffered.”

As the investigation continued, many wondered about regulations that allowed certain companies to keep large amounts of flammable and explosion-prone fertilizers without much oversight into the quality of fire containment systems. The West plant was authorized to hold up to 54,000 pounds of anhydrous ammonia, which the Texas environmental agency considers flammable and potentially toxic, although it’s unknown how much was actually on-site the day of the blast. In addition, its proximity to residences, which meant that an apartment complex, nursing home and houses in a four-block area led many to propose stricter regulation.

A few weeks after, West’s mayor affirmed that they would rebuild, and mourned the 14 lives lost, which included many volunteer first responders.

Texas has opened a criminal probe in the explosion, in part because the cause of the original fire still eluded investigators. By mid-May, authorities said they had ruled down the possibilities to three: a problem with one of the plant's electrical systems, a battery-powered golf cart and a criminal act. This was only possible after picking through the debris piece-by-piece for clues, and eliminating other possibilities, like someone smoking near to flammable materials. While terror had long been ruled out, one paramedic involved in the rescue efforts had been arrested for owning a pipe bomb.

It was then officials announced that 28 to 34 tons of ammonium nitrate exploded, which was equivalent to 15,000 to 20,000 pounds of TNT.

Just a few weeks ago, on December 6, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives reaffirmed that all three possibilities for the original fire were still on the table. One official insisted agents were still on the case, but would not identify what leads they were pursuing. He said, “[The case] will remain open until we've exhausted all leads and all possibilities that we could do.” They did confirm that the paramedic was not involved in the West blast, but wouldn’t give more concrete answers. The investigation will likely continue well into 2014.

This story spurred national interest, but was a popular topic on because it brought up issues about the nature of regulation — more in-depth laws might prevent similar incidents, but are a burden on businesses. On top of that, many were surprised to hear about the gap in oversight for these facilities holding vast quantities of fertilizer. Considering that many other facilities in Texas holding the same material have refused inspections from the fire marshal, the fallout from this incident won’t be leaving the pages of any time soon.