Liberia on Thursday imposed travel bans on 15 people, including the son of ex-president Ellen Johnson Sirleaf, following a probe into the disappearance of new bills worth nearly 100 million US dollars.
The investigation was launched in August after "information surrounding the arrival of containers and bags of moneys" at the port and the international airport of the capital Monrovia, the justice ministry had said.
Travel bans were slapped on Sirleaf's son, Charles, former central bank governor Milton Weeks and Lebanese businessman George Abi Jaoudi, who was close to Sirleaf, the government said on Thursday.
"The government takes the ongoing investigation seriously because it has national security implications," an information ministry statement said.
"Authorities at all ports of entry/exit including land borders, air and sea ports have been directed to take due cognizance of the circular," it said.
The government said initial findings indicate the cash arrived between November 2017, when Sirleaf was still president, and August this year. The current government led by President George Weah took over in January.
"The government has requested the assistance of the United States Treasury Department, the Federal Bureau of Investigation and the International Monetary Fund," the interior ministry said.
The probe has been widened to cover all bills printed since 2016.
Former football star Weah has vowed to crack down on corruption and unveiled in July a series of monetary and fiscal measures to prop up the local currency and tackle inflation.
He announced the central bank was injecting 25 million US dollars into the economy to mop excessive liquidity of Liberian dollars.
In March, Weah said he had "inherited a country that is very broke, depleted by political malfeasance".