Topeka ? The Kansas Department of Corrections said early Wednesday morning that a prisoner disturbance at the Norton Correctional Facility had been resolved.

Department spokesman Samir Arif said the disturbance began around 9:30 p.m. Tuesday when inmates at the prison in northwestern Kansas set fire to a mattress. The disturbance continued outside in the yard, he said, until correctional officers secured all the inmates shortly after midnight.

Norton is a town of about 2,800 people, located 92 miles northwest of Hays.

Tuesday’s disturbance was just the latest in a series of incidents at Kansas correctional facilities.

Officials from the Kansas Organization of State Employees, the union that represents correctional officers, posted statements on social media suggesting that some of the inmates involved in the disturbance were also involved in a June 29 disturbance at the El Dorado Correctional Facility. Sarif, however, said it was too early to determine culpability for the incident, which he said was still under investigation.

As of Wednesday morning, he said, about 90 inmates were being transferred from Norton to other facilities, including Lansing.

Officials from the Kansas Organization of State Employees, the union that represents correctional officers, posted on Twitter around 1 a.m. that the Department of Corrections had canceled a union meeting that had been scheduled at Lansing because of the prisoner transfer.

KOSE officials also tweeted Tuesday night that the disturbance at Norton was more serious than what the Department of Corrections described.

At 11:04 p.m., the union tweeted on its official account: “Huge riot broken out at Norton Correctional Facility. Buildings are burning and some inmates have gotten weapons.”

Arif said no inmates were injured Tuesday night, but two correctional officers received minor injuries that did not require medical attention.

The Norton Correctional Facility houses 856 minimum and medium security inmates. It does not house any maximum security inmates, Arif said.

In addition to the recent incidents at Norton and El Dorado prisons, KOSE executive director Robert Choromanski said there have been a number of incidents at the state prison in Hutchinson in recent weeks, including a series of stabbings and an attack against a correctional officer that resulted in the officer being taken to a hospital. Arif was not immediately able to confirm those incidents Wednesday,

While prisons across the state have been plagued with staffing shortages, Norton has had a relatively low vacancy rate. As of Tuesday, 17 of its 196 uniformed-officer positions were open, or 8.7 percent.

But the number of disciplinary reports on inmates at the Norton prison spiked in August at 396, up 75 percent from the 226 reports in July, according to figures released by the department Tuesday to The Associated Press. The previous peak was 328 reports in June 2016, and last year the prison averaged 209 a month, compared with 245 per month from January through August of this year.

Gov. Sam Brownback announced last month that workers at Kansas state prisons will get pay hikes in the wake of inmate disturbances that have drawn public attention to staff shortages at the facilities. Uniformed officers across the state would receive about a 5 percent raise. Officers at El Dorado Correctional Facility will see raises of about 10 percent.

The department has confirmed three disturbances at the El Dorado facility in May and June involving inmates who refused to return to their cells, as well as two pairs of inmate-on-inmate fights on July 28 that sent one inmate from each altercation to a hospital with stab wounds. Department of Corrections Secretary Joe Norwood has attributed the disturbances to newly arrived inmates who were transferred from other prisons.

All of the prisons struggle with turnover among corrections officers, but the El Dorado prison, east of Wichita, has the highest annual rate at 46 percent, compared with 33 percent for the entire system.

— The Associated Press contributed to this report.