The company that owns the West, Texas, fertilizer plant that exploded last week failed to tell the U.S. Department of Homeland Security (DHS) about the large amounts of ammonium nitrate it was storing onsite, Reuters reported.

The explosion at the West Fertilizer Company plant on April 17 killed 14 people and destroyed dozens of buildings in the small town.

According to filings with the Texas Department of State Health Services, the plant had 270 tons of ammonium nitrate on hand last year. Fertilizer plants and depots are required to report to DHS when they hold 400 pounds or more of the dangerous chemical compound. A failure to report can lead to fines or plant shutdowns, the article stated.

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U.S. Congressman Rep. Bennie Thompson (D-MS) on Friday questioned whether the plant's failure to disclose the information led to the explosion.

"It seems this manufacturer was willfully off the grid," Thompson said. "This facility was known to have chemicals well above the threshold amount to be regulated under the Chemical Facility Anti-Terrorism Standards Act (CFATS), yet we understand that DHS did not even know the plant existed until it blew up."