A pair of state legislators is pushing to stop a St. Paul Park oil refinery from using hydrogen fluoride following a published report that the highly toxic chemical poses potentially catastrophic risks.

In a letter to two state agencies Monday, Rep. Frank Hornstein, DFL-Minneapolis and Sen. Scott Dibble, DFL-Minneapolis, cited documents on file with the U.S. Environmental Protection Agency and reported Sunday by the Star Tribune that showed the refinery’s use of the chemical could, in the event of a major accident, put 1.7 million people in the Twin Cities area at risk.

The 79-year-old plant has never had a catastrophic accident involving hydrogen fluoride, and the worst-case scenarios spelled out in EPA documents — information that is required of refineries — are largely for planning purposes and considered unlikely.

The risks posed by the chemical came to light after an explosion and fire April 26 at the Husky Energy Inc., refinery in Superior, Wis. The blast took place within 200 feet of a hydrogen fluoride tank, setting off fears of a disaster and prompting a mandatory evacuation for large portions of the city of 27,000 people.

No one died in the explosion, but 13 people were injured, six of whom were hospitalized.

In an update Monday, Superior Mayor Jim Paine said debris cleanup — mostly mineral wool and foam insulation — continues at the explosion site and on a nearby roadway, a golf course and in a residential area.

Some 1,315 claims have been filed against Husky for lost wages or other expenses incurred as a result of the explosion and evacuation. No air quality violations have been reported so far, but trace elements of a firefighting chemical have been found in nearby waters, the update said.

In St. Paul on Monday, Hornstein and Dibble sent their letter to the state Department of Public Safety and the Minnesota Pollution Control Agency, saying they want the appropriate state agencies to ask the St. Paul Park refinery to end its use of hydrogen fluoride.

Hornstein, in a phone interview, dismissed the idea that switching from hydrogen fluoride to a safer alternative would be too costly, an argument that oil industry representatives have made in the past.

“I just don’t look at expense as an excuse not to do this,” he said. “They’re making lots of profit. This is a huge facility. And consider the expense of a problem. I think this is a reasonable request.”

A spokesman for the state agencies said Monday that they had no immediate comment.

Hornstein and Dibble also want to know if the facility, which was recently sold by San Antonio-based Andeavor to Houston-based Marathon Oil, has complied with the Emergency Planning and Community Right to Know Act, a 1986 law designed to inform local communities about chemical hazards in their area that was written after the 1984 Bhopal, India, chemical leak disaster.

They’re also seeking information on evacuation and training plans, notification procedures in the event of a leak, and a list of the cities and townships within 19 miles of the refinery.

Numerous refineries use hydrogen fluoride to increase gasoline’s octane, but it’s a poisonous gas that has raised alarms for years.

According to the worst-case scenario on file with the EPA, a massive leak of hydrogen fluoride at the St. Paul Park refinery could create a potentially lethal ground-hugging cloud that could travel up to 19 miles if wind and atmospheric conditions allowed.

Destin Singleton, an Andeavor spokeswoman, told the Star Tribune last week that the worst-case scenarios in EPA documents are “not realistic.”

Like many refineries that use hydrogen fluoride, the St. Paul Park plant has sensors to detect leaks and water systems to suppress them. The refinery’s “water curtains” and “deluge system,” as Andeavor calls them, are meant to capture the hazardous chemical so it doesn’t vaporize. Water can absorb the hydrogen fluoride and “knock it down,” Singleton said.

Seven businesses in Minnesota have hydrogen fluoride on site at eight locations, according to the state Department of Public Safety.

The St. Paul Park oil refinery has by far the largest amount, followed by 3M’s Cottage Grove Center. The remaining locations in Maple Grove, Albertville, Burnsville, Bloomington and Rockford don’t contain enough hydrogen fluoride to warrant filing a risk management plan with the EPA.

Hydrogen fluoride is a fast-acting acid that can cause deep, severe burns or, with sufficient exposure, kill. Exposure can occur through inhalation and skin contact.

The chemical can permanently damage the eyes, skin, nose, throat, respiratory system and bones, according to a 2013 report issued by the United Steelworkers union, which represents many refinery workers.