Thousands of Orthodox Christians are flocking to a church in southwest Chicago to witness what they believe is a miracle.

According to the Chicago Tribune, tiny drops of sweet-smelling oil have been trickling down an icon of John the Baptist at Assumption Greek Orthodox Church in Homer Glen. The parishioners believe the droplets have healing properties.

Parish priest Rev Sotirios Dimitriou – known as Father Sam – said: "The first thing out of my mouth was 'What do I do?' You don't expect anything like this. It's breathtaking. It's so powerful to see such an act of God before your eyes."

The auxiliary bishop of the diocese told the Tribune it would not comment on whether the phenomenon was genuinely miraculous, saying "We let the faithful believe it if they wish." Bishop Demetrios added: "If it brings you closer to God that's wonderful. If it doesn't, it doesn't."

The oil exudes from the icon's halo, wings, hands and beard and is collected in a reservoir of cotton at its base. Dimitriou saturates cotton balls with the substance and hands them out to his parishioners. He has had several reports of divine healing from those who have touched it. One man said a blocked artery had cleared, while another claimed to be cancer free. Dimitriou himself, who had experienced blackouts because of a nerve condition, said he had not suffered since the oil began to flow and had stopped taking his medication.

The Tribune quotes James Skedros, dean of Holy Cross Greek Orthodox School of Theology, who said that similar episodes have taken place across the US. While unlike the Roman Catholic Church the Orthodox Church has no formal process for authenticating them, they are regarded as significant for believers. He said Orthodox Christians believe matter can be a conveyor of sanctity.

"We have a very different understanding of matter as a vehicle of holiness," Skedros said. "We put [icons] on walls, burn candles in front of them, light incense in front of them because they're images of what they represent — the holy person or image of Christ or the saint."

Meanwhile the church itself is struggling with the number of visitors it is receiving because of the phenomenon. A statement from the diocese said: "We are blessed to have this occurring at our parish in Homer Glen, Illinois.

"We ask for patience and understanding when wanting to visit this icon or request additional information as this is a small community parish that is trying to work out how best to share this blessing with now a much enlarged audience."