The Swiss authorities have agreed to freeze any bank accounts belonging to Liberian leader Charles Taylor.
Both sides accuse the other of violating the ceasefire
This follows a request from the United Nations-backed war crimes court in Sierra Leone.
It is not known how much money may be involved at this stage.
Meanwhile, the government and rebels in Liberia have traded allegations over breaches of their ceasefire in the civil war signed last week.
Liberian Information Minister Reginald Goodridge said on Monday the town of Ganta, on the border with Guinea, had come under tank fire and he alleged that rebels there were being helped by Guinean forces.
We will work to disentangle Taylor's finances and identify the profits he reaped from his criminal activity
War crimes prosecutor
He said the shelling was causing chaos, forcing thousands of people to flee the region.
The UN-backed Special Court for Sierra Leone has indicted Mr Taylor for alleged war crimes during the brutal, decade-long civil war, which ended last year.
"The money may be evidence of the joint criminal enterprise that we allege Taylor, with several other indictees, conducted in Sierra Leone over a period of years," said David Crane, prosecutor of the Special Court for Sierra Leone.
"In conjunction with the Swiss, we will work to disentangle Taylor's finances and identify the profits he reaped from his criminal activity here".
There have also been allegations from the Liberian Government that forces from Sierra Leone were helping rebel attacks on Monrovia - rejected as "absurd" by the Sierra Leonean ambassador in the city.
And the rebel groups claim that they have been attacked by government forces ignoring the ceasefire.
The allegations follow a delay in the arrival in Liberia of the ceasefire verification team, which is meant to map the precise locations of the different fighting factions.
The team - made up representatives from all sides along with international monitors - was due to arrive from Ghana on Saturday.
A West African-led peacekeeping force of at least 2,000 troops is due to oversee the peace accord once the locations of the factions are verified.
On Friday President Charles Taylor said he did not intend to step down before his term ends next year and may seek re-election - despite his exclusion from power under the peace agreement.
Indicted on war crimes charges
Under UN sanctions
Won 1997 elections
Mr Taylor's position is seen as key to the future peace of Liberia, where fighting has spread chaos into neighbouring states.
"I said I was prepared to step aside," said Mr Taylor in his broadcast, emphasising "prepared".
"I didn't say I was not going to run."
Mr Taylor argued that he had a large following in Liberia and that many people in authority - like local chiefs - were protesting that he could not step aside without their approval.
The ceasefire set a 30-day deadline for a comprehensive peace deal and transitional government without Mr Taylor.
At the time of the negotiations he also sought assurances that the war crimes indictment would be dropped if he were to step down.