(CNN) -- A helicopter, its passengers and crew -- initially reported to have been seized Tuesday by rebels in the Sudanese territory of Darfur -- have returned unhurt to the town of Nyala, Sudan, the Russian airline UTair Aviation said on its website.
It said "Sudanese authorities" had detained the helicopter, but It was not immediately clear what the circumstances were.
The helicopter was carrying four Russian crew members and five Sudanese passengers, according to the Russia's Foreign Ministry. They returned shortly before 8 p.m.
"UTair, together with the Russian Embassy and the U.N. representatives in Sudan, are taking necessary measures to clear up the situation," UTair's statement said.
The company said the helicopter was conducting a U.N.-commissioned flight on Monday from Al-Fashir, Sudan, to Abeche, Chad, and that the passengers and crew "were detained by the Sudanese authorities during a stopover."
UTair has been a transport contractor for the United Nations' peacekeeping missions since 1991 and is the largest U.N. provider for helicopter services, the company said in a news release.
Earlier, a spokesman for the Russian Embassy in Darfur, Yuri Vidakas, told Russia's Interfax news agency that the incident was not an abduction. He said it was more likely that the helicopter landed in the wrong place due to a navigation error.
The craft was flying for the joint peacekeeping mission by the United Nations and the African Union in Darfur.
Conflict in the Darfur region has uprooted as many as 2.7 million Darfurians and left about 300,000 people dead over the past seven years.
Earlier Tuesday, the German Foreign Ministry announced the release of two German nationals who were kidnapped in Sudan last month.
CNN's Maxim Tkachenko contributed to this report.