Ferguson travelled to Japan after being contracted by the Japanese rugby union team the NEC Green Rockets Tokatsu.
“Blake Ferguson, a contract player belonging to NEC Green Rockets Tokatsu, was arrested on December 30 on suspicion of possessing illegal drugs,” the club said in a statement.
“We deeply apologise for causing a great deal of concern and inconvenience to everyone involved.
“Our team fully cooperates with the police investigation and strives to understand the situation.”
Local media reports Ferguson was searched by police after allegedly assaulting another patron in the Tokyo district of Roppongi.
Police allegedly found cocaine.