The cause of the spill, which occurred on Wednesday, is being investigated, the director general of ports and maritime in Iran's Bushehr Province, Siavash Arjomandzadeh, told the official IRNA news agency.
The cleanup took place near the Abuzar field, Iran's main production area in the Gulf.
An Iranian official had told IRNA on Thursday that it was difficult to determine the cause of the spill because there were several fields belonging to Iran and other countries in the region. He said oil could have leaked from underwater pipelines.
Abuzar oil field, about 75 km (46 miles) west of Iran's Kharg Island, has three main platforms producing between 195,000 to 220,000 barrels per day of oil, IRNA reported, adding 107 wells had been drilled in the field of which 67 still operated.