Last week, U.S. Rep. Ted W. Lieu (D-Calif.) and Rep. Maxine Waters (D-Calif) sent a letter to the chairman Rafael Moure-Eraso of the U.S. Chemical Safety Board (CSB) requesting that the agency investigate the root causes of the Feb. 18 explosion at the ExxonMobil refinery in Torrance, and make recommendations to increase refinery process and public safety.

The February incident, which hospitalized four workers and covered the surrounding residential neighborhoods with “catalyst dust,” was the third explosion in the Torrance refinery’s history and the third explosion at a U.S. refinery this year.

A CSB investigation would contribute to Congress’ understanding of why U.S. refineries have a significantly higher accident rate than those in Europe, the representatives said.