Authorities say they’re testing the air quality after a pipe ruptured, prompting the evacuations of more than 300 residents and sending dozens of people to hospitals.

The Mississippi Department of Emergency Management said 46 people were treated at area hospitals after the Saturday night rupture, but all of them had been released by late Sunday morning.

Authorities said the 24-inch pressurized pipe ruptured in a heavily wooded area near Satartia, about 40 miles (64 kilometers) northwest of Jackson.

They say the pipe contained carbon dioxide and hydrogen sulfide and that residents in the area complained of green gas and a noxious odor.

Residents were expected to be able to return to their homes soon, emergency officials said in an update late Sunday morning.

It appears the ground caved into a ravine, damaging the 24-inch pipe, the state agency said.