Afkham expressed sympathy with the families of the four Saudi pilgrims who lost their lives as a result of poisoning.
Foreign Ministry Spokeswoman Marzieh Afkham said Iran is sorry about what happened to a number of Saudi pilgrims in the holy city of Mashhad.
Talking in her weekly press briefing, she further expressed sympathy with the families of the four pilgrims who lost their lives as a result of poisoning.
She noted that officials have been working on the case in earnest to discover the cause of the incident.
According to the spokeswoman, a number of people have been arrested in this connection.
Four Saudi citizens died from poisoning in a hospital in Mashhad, in the northeastern Iranian province of Khorasan Razavi.
The incident on Sunday sent 33 Saudi pilgrims to the hospital with poisoning symptoms.
Four Saudi children lost their lives despite extensive treatment by Iranian medical staff.
On a short visit by Iranian Foreign Minister Mohammad Javad Zarif to Oman, Afkham said the visit took place to discuss a number of regional issues with Omani officials including the Yemen crisis.
She said the trip was short and compact but fruitful.