Some Christians claimed they saw blood oozing out from the heart of Jesus in the picture. They believe it to be a miracle.
However, a spokesperson for the Catholic bishop in Mumbai has brushed off the claims saying that the dark patch is the result of moisture in the air.
Father Donat D'souza of St Michael's parish said that parishioners noticed it soon after the last service performed on Friday evening.
It might have been caused by moisture," he acknowledged.
The church claims to have welcomed over 100,000 visitors hoping to catch a glimpse of the picture since news of the patch emerged. Some even waited for hours to touch the picture, the church said.
Father Gregory Lobo, secretary of the Bombay Archdiocesan Board of Education, said there was nothing wrong in calling it a "miracle" so long as it changes people's lives.
It is a "matter of faith", he said.
The image has been sent for scrutiny and may even be sent for a lab testing.