MOSCOW (JTA) — Thirteen Chabad yeshiva students were deported from Russia over the weekend following a visa incident that prompted a rare case of direct intervention by the U.S. State Department.

The students, who were studying in the provincial city of Rostov, about 1,000 miles south of Moscow, were detained on immigrations violations stemming from their failure to properly register with authorities upon their arrival.

Mostly from the United States and Canada, the students were arrested just before Shabbat on Friday. Early the next morning, at the urging of Jewish groups concerned about their safety and the conditions in which they were being held, two U.S. diplomats based in Moscow flew to Rostov to secure their release.

“The U.S. Embassy did a fantastic job in resolving this whole issue, ” said Mark Levin, executive director of the Washington-based NCSJ, which focuses on issues in the former Soviet Union. “They responded basically in the middle of the night to our request to intervene, and they did. “

Rabbi Yosif Groner, a Chabad rabbi in Charlotte, N.C., whose 20-year-old son Mendel was among those detained, said the arrests followed a police raid the previous day on the yeshiva.

“The government agents came to the school and they confiscated the passports and said that there was a question of the validity of the visa or registration, ” Groner told JTA.

Rostov has special significance for Lubavitchers, as it was the final home and burial place of Sholom Dovber Schneerson, the fifth Lubavitcher rebbe. Many of the students in the yeshiva are the children of prominent Chabad rabbis abroad.

Although no one would speculate about the cause of the students’ detention, the arrests come at a time of heightened tension between Washington and Moscow over issues ranging from a proposed missile-defense shield in Eastern Europe to Russia’s perceived intransigence over the Iranian nuclear crisis.

One recent manifestation of this tension is a tightening of the visa policy. All foreign visitors to Russia are required to register with the police within three days of their arrival, but the law is applied sporadically and usually results in a simple fine.

While no one is disputing that the students were not properly registered, the heavy-handed approach of the authorities raised eyebrows here.

Following a brief arraignment on Saturday, the students were ordered into detention pending their deportation. Faced with breaking the Sabbath, they pleaded to be allowed to walk the 45 minutes to a dilapidated local prison rather than take the 90-minute drive to a prison for foreigners.

In the local prison, the detainees were forced together into a tiny cell meant to house three prisoners, according to several sources who spoke to the students, all males. The room was furnished with plywood beds and a hole in the center of the room meant to serve as a toilet.

Russian prison conditions are considerably poorer than in the West; abuses are considered to be widespread.

“I just don’t understand why they were treated so harshly, ” said Groner, whose grandfather was imprisoned in a Soviet gulag for running a Hebrew school in the 1930s. “It brought back memories of people in the olden days of communist Russia, and that was disturbing. “

Upon learning of the detention Rabbi Berel Lazar, a chief rabbi of Russia and head of the Chabad-led Federation of Jewish Communities, unsuccessfully appealed to the Russian government for the stduents’ release. At that point the NCSJ, working closely with Chabad’s representative in Washington, Rabbi Levi Shemtov, used its contacts at the State Department to urge intervention.

Two U.S. diplomats in Moscow — the deputy counsel general, Pat Walsh, and counselor assistant Igor Krivoshy — flew to Rostov to secure the students’ release. The students arrived safely in Israel on Sunday after crossing the border into Ukraine by bus under the direct charge of the U.S. government.

The failure of Lazar, considered a political insider and friend of President Vladimir Putin, to secure their release poses many questions about why the yeshiva was raided in the first place.