Immigration controller Chulananda Perera says they are members of Tabligh Jamat, a group founded in India to spread the teachings of Islam.
He said Monday they arrived in Sri Lanka as tourists but were found to be propagating Islam in several parts of the country.
Perera said they include citizens of India, Pakistan, Bangladesh, Maldives and some Arab countries.
About 7 percent of Sri Lanka’s 20 million people are Muslims. About 74 percent are Sinhalese, who are mostly Buddhists, while about 18 percent others are Tamils, who are predominantly Hindus or Christians.