After a disturbance at the Tecumseh state prison in southeast Nebraska on Thursday afternoon, two prison inmates have been confirmed dead. According to prison officials, several other inmates were affected with non-life threatening injuries and around 40 inmates of a unit with 128 prisoners had been involved in the disturbance.

Reportedly the prison was on lockdown for several hours, with the inmates refusing to return to their cells. There are reportedly no details available as to the cause of death to the two inmates, who were found inside the housing unit, and no cause was given for the disturbance.

As reported by Metro, Department of Correctional Services Director Scott Frakes said the incident is a reminder that prisons are a “dangerous business.” The Independent reports that Dawn-Renee Smith, a spokeswoman for the department, had said an emergency response team had secured the prisoners and had extinguished a fire which had been set a prison yard.

Reportedly the disturbance was isolated to half of the prison housing unit, along with the small fenced yard. The lockdown was announced by Smith at around 2:45 pm and reportedly by 5:30 pm the housing unit was once again “habitable and secure.” Governor Pete Ricketts said in a statement that the disturbance was quickly resolved and that public safety was never at risk.

However, he did say Director Frakes will be thoroughly investigating the incident, and the inmates who were involved, and the loss of life would be prosecuted to the full extent of the law.

Same housing unit involved in 2015 riot

The same housing unit involved in the current disturbance was the site of a riot in May 2015, where around $2 million in damage was caused.

That riot left several staff members injured and reportedly involved several hundred of the inmates, with the disturbance caused in three living units, along with a gym and courtyard.

At that time, an investigation showed prisoners were trying to air their grievances about what they believed to be perks received only by certain inmates of the prison, along with disrespect shown by inexperienced prison staff members.

Prison guards watched inmates from behind a fence

As the incident unfolded, the scene was watched by prison guards, secure behind a razor wire fence, as the inmates could be seen waving their arms in the yard, with smoke billowing around them and a helicopter circling overhead. Reportedly both country and state officials were involved at the scene, together with the prison’s own emergency response team.

Fire fed by mattresses thrown into prison yard

According to Mike Marvin, head of the union that represents prison workers, he had been told inmates had thrown mattresses onto the fire in the prison yard, but he said he didn’t know the cause of the inmates’ protest.

Meanwhile along with the investigation to be run by Director Frankes, Doug Koebernick, an inspector general involved in the corrections department, is also planning a full investigation into the circumstances surrounding the incident.