U.S. Senator Barbara Boxer said this week that the Environment and Public Works Committee she chairs will investigate the devastating West, Texas fertilizer plant explosion that killed 14 people – many of them first responders – on April 18^th.

The Chemical Safety Board (CSB), EPA and OSHA are also looking into the tragedy, whose cause is still unknown. Inquiries are also being made by a Texas state House committee and the state panel on Homeland Security and Public Safety.

Boxer, a California Democrat, said the panel will look at possible gaps in the enforcement of U.S. chemical safety regulations.

In a letter sent to the EPA on Tuesday, Boxer requested information on that agency’s planned investigation, including its timeline and scope.

She also asked why ammonium nitrate – which was reportedly stored at the fertilizer plant in large quantities and may have caused the explosion – is not one of the chemicals that facilities are required to report to the EPA under the Risk Management Program.

Companies are required by law to report whether they are storing substantial amounts of ammonia nitrate to the U.S. Department of Homeland Security – something West Fertilizer Co., the operator of the plant, reportedly did not do.

"I cannot rest until we get to the bottom of what caused the disaster in West, Texas and the tragic loss of life," Boxer said in a statement. "It is critical that we find out how this happened."