Earlier, local officials had said they were members of the elite Revolutionary Guards force, but later reports made no reference to this.
The Iranians were detained near Mashkel district, after shooting out the tyres of the smuggler's car, reports say.
Iranian state TV says some of the men were "border guards hunting smugglers who had accidently entered Pakistan."
A Pakistani security official said the Iranians were arrested about four miles (seven km) from the border with Iran.
Pakistan officials said the detainees had been travelling in two cars without travel documents.
"The guards have been handed over to the Iranian authorities because it's found that they crossed into Pakistan mistakenly," a spokesman for Pakistan's Frontier Corps paramilitary force was quoted as saying by Reuters news agency.
The arrests had come just over a week since a suicide bomb killed 42 people, among them six Revolutionary Guard commanders, in Iran's Sistan-Baluchistan province.
Iran said a Sunni militant group had launched the attack from Pakistan. Islamabad denied any involvement.
