Twenty-six people were killed when a bus carrying female students overturned in south-western Iran, state radio has reported.
Senior police official Colonel Mohammad Reza Mehmandar was quoted as saying that the driver lost control of the vehicle because of high speed in rainy weather.
Col Mehmandar said 19 other people were injured in the crash and were rushed to hospital for treatment.
The accident happened on the Izeh-Lordegan road, about 310 miles south-west of the capital, Tehran.
Iran has one of the world's worst traffic safety records, with more than 400,000 accidents and about 20,000 deaths on its roads every year.
The high death tolls are blamed on high speed, unsafe vehicles, widespread disregard of traffic laws and inadequate emergency services.