Gibbs said the move was a law enforcement matter — and that law enforcement "acted appropriately."
Obama and Russian President Dmitry Medvedev have hailed what they called a "reset" relationship between their nations.
Russian leadership has expressed frustration about the arrests and called them unfounded. Gibbs said relations will not take a hit.
Gibbs said Obama was aware of the investigation before he met with Medvedev at the White House on Thursday.
The two leaders did not discuss the issue, Gibbs said.