Dense fog may have been a factor in a two-vehicle, head-on collision that sent four people to the hospital over the weekend.

Sheriff's officials said Mark Halsey, 64, of Eldora, was driving an SUV in which Eric Halsey, 39, of Eldora, was a passenger. Authorities confirmed the other SUV was driven by Dennis Wilke, 65, of Altoona, and in his passenger was Rosanne Wilke, 61, of Altoona.

The two drivers and their passengers were all taken to the hospital in Grundy Center for treatment.

According to Grundy County sheriff's officials, there was dense fog at the time of the crash.

Authorities are investigating the accident, which occurred around 11 AM Sunday on Iowa Highway 14 ("G" Ave.) about eight miles northwest of Conrad.