A lightning strike sent 16 inmates at an Ohio state prison to the hospital the evening of Aug. 11, authorities said.

Lightning struck at the Grafton Correctional Institution in Grafton, Ohio, about 30 miles outside of Cleveland, according to the Ohio Department of Rehabilitation and Correction.

The 16 inmates were transported to an outside hospital, including one who was life-flighted, the department said in a statement posted to social media. In an update on Aug. 12, the department told USA TODAY that nine of the inmates have returned to the facility. One is still hospitalized in serious condition, and six others are hospitalized in stable, nonlife-threatening condition. There were no deaths and no injuries to staff as of Aug. 12.

At the time of the strike, the inmates were “returning from the evening meal,” the department said. It was not clear where they were when they were injured.

There was a severe thunderstorm watch in place the evening of Aug. 11 through about 8 p.m. ET in northwest and north-central Ohio, with the main hazard identified as wind gusts of over 60 mph, according to the National Weather Service Office in Cleveland.

Each year, about 37 million lightning strikes hit the ground in the United States, and an average of 400 people are struck. The odds of it happening are about 1 in 1.2 million, according to the National Weather Service. Though almost 90% of all lightning strike victims survive, 517 people died between 2006 and 2025 in the country, according to the Centers for Disease Control and Prevention.

This story has been updated to add new information.