The forensic team found traces of kerosene inside the church premises, which led the police to conclude that the attack was pre-meditated.
A case of "mischief by fire" has been lodged and the police are questioning several persons, among them the watchman of the church.
The police will come out with a final report after the forensic team finalises its findings.
The authorities found out about the fire around 6.30 am after the watchman, who came in for work around that time, informed them. There was no security guard at the church between 5 and 6 am, which was when the authorities thought the fire started.
There was no casualty since the church was empty at the time.
"It seems to be a deliberate act as we could smell kerosene on the spot. It has been a very emotional day for us," Father Stanley Kozhichira, of the Delhi archdiocese told NDTV.
"We are not blaming any particular group for the act. It has been done by anti-social elements. We want swift action by police", Chancellor of Delhi Catholic Church archdiocese, Father Mathew, told NDTV.
The church was built in 2001. Almost 3000 people attend the Sunday mass.