"An emergency response team from the local Red Cross and one member of the international Red Cross were detained. They are now all free," said the official.
The international staff member is Swiss, the official added.
"The latest information that we have is that they were released," the official added.
Earlier, Kiril Rudenko, deputy spokesman for the self-proclaimed "People's Republic of Donetsk", said the Red Cross workers had been detained because the rebels thought they were spies.
A spokeswoman for the International Committee for the Red Cross in Geneva said: "Our colleagues were apparently taken, but then they were let go."
"As we speak now, everyone has been released," she said, adding that the organisation was trying to verify the number of Red Cross workers taken and their nationalities.