The Rubicon LLC complex in Ascension Parish had a small release of potentially toxic phosgene gas Wednesday that did not escape the company’s plant site off River Road, parish authorities said.

Dutchtown High School, which is a few miles north of the parish’s chemical zone along the Mississippi River, began to shelter in place as a precaution at 2:23 p.m. The shelter-in-place order was lifted about 15 minutes later, according to school email sent to parents.

Lt. Col. Bobby Webre, sheriff’s chief of criminal operations, said three other schools also were advised to shelter in place: Dutchtown Primary and Middle schools, which are across La. 73 from the high school, and nearby Spanish Lake Primary on Bluff Road.

Jackie Tisdell, school system spokeswoman, said those three schools were in the process of notification and sheltering in place when the all-clear was given.

Capt. Cody Melancon, commander of the sheriff’s Hazardous Materials Team, said the leak was reported about 2 p.m. and the all-clear came at 2:29 p.m.

Phosgene, a colorless gas that smells like freshly cut grass or hay, was once used as a chemical weapon during the European trench battles of World War I and is important in modern-day production of pharmaceuticals and polyurethanes.

The gas can cause choking and coughing. If someone is exposed to it in high enough concentrations and over a long enough duration, a person can asphyxiate.

Melancon said company officials reported that plant site monitors showed the small amount of gas did not leave the site. He said it was not clear how much phosgene had been released, however.

Rick Webre, director of the parish Office of Homeland Security and Emergency Preparedness, said he was trying to find out why the schools sheltered in place because the chemical release did not pose an off-site risk.

Rubicon, a joint venture of the Huntsman and Chemtura corporations, covers 81 acres inside Huntsman’s 760-acre complex in Geismar. Rubicon produces adhesives, coatings, polyurethane insulation, footwear, molded plastics and pharmaceuticals, the Huntsman website says.