(CNN) A witness in the trial of an Indian Catholic bishop accused of raping a nun has died, according to police, prompting a probe into his death.

Father Kuriakose Kattuthara was around 62 years old, police said. He died just weeks after giving his testimony in the case against Bishop Franco Mulakkal, who has been accused of raping a nun on multiple occasions over two years.

Mulakkal, who is based in northern Punjab state, is accused of raping the nun during visits to Kerala state in the south of India. He denies the charges and is currently out on bail, awaiting trial.

"He (Kattuthara) passed away last night. We are going to investigate the circumstances around his death and there will be an autopsy," said A.R. Sharma, a senior police official in Punjab.

Kattuthara was a priest in the village of Dasuya in Punjab. He was among dozens of witnesses who are due to testify in Mulakkal's trial in Kerala.

The case is a rare example of a nun publicly accusing a Church superior of wrongdoing.

Mulakkal's arrest in September followed weeks of protest by nuns in Kerala calling for his prosecution.

Last week, a local court in Kerala granted him bail, attaching the condition that he leave the state, except for his appearances before investigators. Following his release, he returned to Punjab to a hero's welcome, with supporters cheering as he made his way home.

Claim of 13 instances

The 44-year-old nun, who has not been named, first filed a police report in June, accusing Mulakkal of raping her 13 times between 2014 and 2016. She alleged the abuse occurred while Mulakkal was staying in Kerala in a guest house belonging to the St. Francis Mission Home.

At the time, Mulakkal was the bishop of Jalandhar, a city in Punjab. His diocese said the bishop was a frequent visitor to Kerala for church-related events.

Earlier in August, an advocacy group filed a petition on behalf of the nun, asking for the immediate arrest of Mulakkal, but the Kerala High Court declined to intervene, saying the delay in bringing charges was understandable given the amount of time that has passed since the alleged abuse. As the case dominated headlines in India, Mulakkal temporarily stepped down from his position in September.

It was the second time in two months the nun's supporters had unsuccessfully petitioned the court to intervene, leading to renewed accusations that state politicians and Catholic leaders were working behind the scenes to suppress the case.

The Catholic Church has been battling allegations of sexual abuse around the world, especially against minors, for years. In an unusually blunt letter released last month, Pope Francis acknowledged that the church had historically failed to address properly wrongdoing by priests.

Christianity is a minority religion in India, practiced by 2.3% of the population, according to the most recent census data, but Kerala is home to a sizable Christian community that dates back hundreds of years. The majority are Catholics.

According to recent government figures, the southern state is home to more than 6 million Christians, or 19% of the population. Communities there draw their heritage from Thomas the Apostle, who is traditionally believed to have traveled to India to preach the gospel in the first century.