He, however, said Syria is "keen" to send them home if they are found in its territory.
Mr Abbas said an Indian delegation has made several trips to Syria and Iraq in the past to seek information about them and the chief of the Intelligence Department of Syria has also visited New Delhi in this regard.
"The Indian delegation went to Syria many times and the chief of Syrian intelligence agency came to Delhi for it," the envoy said.
"We are very keen to bring them (missing Indians) home if they are in our territory, but there is no official confirmation about it," he added.
Early this month, Iraqi forces freed Mosul from the ISIS, a development that gave a ray of hope to the families of 39 Indians.
The statement by Syrian Ambassador comes days after Minister for External Affairs, Sushma Swaraj explained in both houses of Parliament that India has no evidence of the missing Indians in Iraq being dead or alive. And in absence of "solid proof", it is a "sin" at personal level and irresponsible act on the part of the government to declare them dead, Ms Swaraj had said.
The government has sought help from other countries too, but there has been no development yet. "We are not sitting idle. All countries which can help have been asked for help," she said and added, "Why will I mislead? What will I gain? What will I gain, what will my government gain by misleading?"
Her deputy V K Singh had travelled to Iraq on the very next day ISIS was overthrown from Mosul on July 9 this year.
So far, only Harjit Masih has returned successfully from captivity under ISIS in the restive city Mosul.
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