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, including Arkema, said the rule could make it easier for terrorists and other criminals to target refineries, chemical plants and other facilities.

Get Breaking News Delivered to Your Inbox

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.

Stanislaus, who led the EPA's Office of Land and Emergency Management during the Obama administration, disputed critics who said the rule would have made it easier for terrorists to gain information about hazardous chemicals.

The rule "struck a balance" between the public's right to know important safety information and national security concerns, he said.

An EPA spokeswoman said the agency's Risk Management Program rule continues to be in effect and requires facilities that use extremely hazardous substances to develop plans that identify potential effects of a chemical accident, steps to prevent an accident and emergency response procedures.

"The agency's recent action to delay the effectiveness of the 2017 amendments had no effect on the major safety requirements that applied to the Arkema Crosby plant at the time of the fire," spokeswoman Amy Graham said.

EPA is providing assistance and resources to the first responders in Harris County and the Federal Emergency Management Agency, Pruitt said in a statement. Data received from an aircraft that surveyed the scene early Thursday "indicates that there are no concentrations of concern for toxic materials reported at this time," he said.

The EPA issued a final rule in January, seven days before President Barack Obama left office. The EPA said at the time that the rule would help prevent accidents and improve emergency preparedness by allowing first responders better data on chemical storage.

A coalition of business groups opposed the rule, saying it would impose significant new costs without specific safety benefits. The rule "may actually compromise the security of our facilities, emergency responders and our communities," groups including the American Chemistry Council, the American Fuel & Petrochemical Manufacturers and American Petroleum Institute said.

Arkema also lobbied against the rule, telling the EPA in a May 2016 letter that the proposal "will likely add significant new costs and burdens" and "could create a risk to our sites and to the communities surrounding them."

Stanislaus called the rule "a modest first step" to address safety for first responders and localities. The rule came after a three-year process that included eight public hearings and more than 44,000 public comments, he said.