Investigators visited Texas plant twice in weeks before explosion

WEST, Texas Texas state investigators visited a fertilizer plant twice in the weeks before a deadly explosion at the site.

Officials from the Texas State Chemist attended the West Fertilizer plant as many as ten times a year over the past decade, CBS Dallas reported.

The most recent visit was prompted by a request by the plant's manager, to investigate a product that didn't look right.

The plant received several violations over the years, usually for fertilizers that did not contain exactly the right chemical mixture.

However state chemist Dr Tim Hermann said West's violations were a bit better than average for a company that size.

At least 14 people were killed and 200 injured after the April 17 blast in the tiny Texas town of West.

• Obamas to attend memorial for Texas explosion victims
• Debris litters area outside Texas plant, explosion church holds service in hayfield
• Majority of deaths in West Texas explosion were first responders

Chemical inventory sheets filed with the state Department of Health Services show there was as much as 270 tons of flammable ammonium nitrate on the property, 135-times more than was used in the Oklahoma City bombing.

Investigators said they were excavating a crate left at the site of the explosion. They are also doing 3-D imaging to obtain an accurate measurement of the crater. They described the work as similar to an archaeological dig, going layer by layer through the ground.

Despite the chemicals on the West Fertilizer site, locals did not necessarily suspect the plant was responsible when the explosion happened.

"I knew the fertilizer plant was on fire, but then I knew we've got all this construction going on on the highway," said West resident Krystal Vanek. "So then I wasn't sure if something blew up at the construction, or if it was the fertilizer plant that actually blew up."