WASHINGTON — The Trump administration delayed an Obama-era rule that would have tightened safety requirements for companies that store large quantities of dangerous chemicals such as the chemical plant near Houston that exploded early Thursday.

The Environmental Protection Agency rule would have required chemical plants, including the now-destroyed Arkema Inc., plant outside Houston, to make public the types and quantities of chemicals stored on site. The rule was developed after a fertilizer plant in West, Texas, exploded in 2013, killing 15 people.

EPA Administrator Scott Pruitt prevented the safety rule from taking effect until 2019 to allow the agency time to reconsider industry objections. Chemical companies and other business groups said the rule could make it easier for terrorists and other criminals to target refineries, chemical plants and other facilities.

Environmental groups and 11 states are fighting the delay in court.

Arkema has not released a full list of chemicals stored at the plant, although officials said the substances that caught fire were organic peroxides, a family of volatile compounds used for making a variety of products, including pharmaceuticals and construction materials.

Mathy Stanislaus, a former EPA assistant administrator who helped draft the rule for the Obama administration, said it probably would not have prevented the explosion but could have greatly reduced the risk to first responders. The Harris County sheriff says 15 deputies sought medical attention for eye irritation after the fire, although most were quickly treated and released.

“There was a gap in specific knowledge. People need to know what chemicals (are being stored) and what kind of precautions are in place,” Stanislaus said in an interview Thursday.