The daily Javan newspaper, which has ties to the elite Revolutionary Guards, reported that the five included Niki Khanjani, who is the daughter of Jamaloddin Khanjani, one of seven Baha'i leaders jailed since 2008 on charges of harming national security.
The report did not describe the current charges, but said many Bahais have escaped to neighboring countries and the remote border areas of Iran after allegedly fomenting postelection unrest.
Opposition members have poured into the streets on several occasions since June in protest to the result of the presidential election, which they maintain were tarnished by fraud.
Iranian authorities have repeatedly accused members of Bahai minority of being involved in the turmoil.
In January, the Tehran prosecutor said several followers of the Bahai faith were detained in December protests for "organizing the riots and sending pictures of the protest abroad."
The minority has also been pursued for its faith, banned in 1979 after the Islamic revolution.
The Baha'i faith was founded in the 1860s by Baha'u'llah, a Persian nobleman considered a prophet by his followers. Islam considers Muhammad the last of the prophets and so conservatives reject the Bahai faith.
Previously there had been reports that as many as 48 Bahais were imprisoned in Iran solely on the basis of their religious beliefs.