Political insiders say Monday’s mysterious unblocking of Facebook and Twitter was an attempt by certain groups within the Iranian political establishment — it was not clear exactly who — to measure the reactions of Internet users.

“Monday’s move was a test conducted to see what people would do if Facebook and Twitter were opened,” said one source close to the new government who asked to remain anonymous because of the secrecy surrounding the matter. “Apparently the test results have been unfavorable, because the sites have been closed again.”

That was echoed by Farshad Ghorbanpour, a political analyst close to the government. “It seems to me the authorities wanted to see what would happen if the Web sites were opened,” he said. “This is not uncommon in Iran.”

It was unclear exactly what the authorities would have been seeking to find out with such a test.

Conservatives tended to favor a technical glitch as the explanation for the unblocking of the Web sites. “God willing this has been a mistake,” Judge Abdolsamad Khoramabadi, a prominent hard-liner, told the semiofficial Mehr news agency. “But if this was done on purpose, we will confront those behind it.”

Judge Khoramabadi warned on Sunday that Facebook is destroying families, saying that it is the cause of one-fifth of all divorces in the United States. “Some officials seem to be unaware of the dangers of this Web site when they speak of unblocking it,” he told the Khabaronline Web news site.