The four Saudi pilgrims who recently lost their lives in northeastern Iran had been poisoned due to fumigation, Iran�s health minister says.

Symptoms of poisoning were seen in the blood samples of the patients, Hassan Hashemi said on Monday, adding four of them had died by Sunday night.

He added that the incident occurred as a result of fumigation in the apartment hotel where a group of 33 Saudi pilgrims were staying.

The Iranian minister noted that the poisoned Saudi pilgrims received immediate and adequate treatment in hospitals in the holy city of Mashhad in Khorassan Razavi Province.

He urged an immediate probe into the incident, saying the results of the investigation should be announced accordingly.

Hashemi also called for severe punishment for those responsible for the incident, saying, �This is what the [Iranian] nation expects.�

Head of the Imam Reza hospital in Mashhad Abdollah Bahrami said on Sunday that the incident happened earlier in the day when the Saudi pilgrims were hospitalized with poisoning symptoms.

He added that four Saudi children lost their lives despite extensive treatment by Iranian medical staff.

Meanwhile, Mashhad Prosecutor Gholam Ali Sadeqi also said a probe had been launched into the case.

"A special inspector has been designated to immediately look into all aspects and probable causes of the incident," said the prosecutor.

The preliminary investigation rules out foul play in the deaths of the Saudi nationals, he noted.

Mashhad is the spiritual capital of Iran and it owes its significance to the Imam Reza shrine, which draws almost millions of pilgrims from around the world every year.

By Press TV