NEAR RAYMONDVILLE - A state agency said the driver of a prison bus may have been driving at an unsafe speed before it veered off the road and rolled over in Willacy County Friday morning.

Department of Public Safety Lt. Johnny Hernandez told CHANNEL 5 NEWS 16 inmates aboard the bus survived the accident without major injuries. Two of them are still hospitalized in Harlingen for precautionary measures.

The bus was traveling from the Segovia-Lopez facility in Edinburg to the state jail in Raymondville. Lt. Hernandez said the slick roads and dense fog were factors in the crash.

Willacy County Sheriff Larry Spence was one of the first responders in the scene Friday morning. He said in these types of situations, additional law enforcement gets to the location immediately to try and keep prisoners cuffed at all times.

 “We keep them shackled in the legs and everything. We send somebody with the ambulance if it’s going down there. In this particular incident, I think people from the prison itself followed the ambulance,” he said.

Sheriff Spence said the prisoner transport bus was headed toward the prison three miles down the expressway.

“While I was standing out there today directing traffic, trying to keep others from getting hit and making a bigger accident, I was amazed at the number of people that were coming up with no headlights on,” he said.

Sheriff Spence said it’s just one more reason to slow down when driving in the fog.

DPS said two state employees were also taken to Harlingen Medical and Valley Baptist. A hospital spokeswoman declined to comment about the incident.

Texas Correctional System spokesman Jason Clark said all the injuries were minor. The bus driver and another state employee were treated and released from the hospital.

Clark added there is no significant cost impact. He said prisoners were simply being taken from one state prison facility to another.