The Department of Transport has confirmed that none of the additional €36m funding that was pledged to CIÉ has been paid so far.
The Cabinet authorised the department to allocate the extra money to CIÉ in July to protect public transport services.
A department spokesman said: "The Government is exploring alternative ways to make up the shortfall other than Exchequer funding, including the sale of non-core assets and new credit facilities."
He said CIÉ was working "to develop a business plan that will allow the company to operate on a financially sustainable basis in the coming years".
CIÉ said: "The means by which the supplementary funding for this year of €36m is provided is a matter for the Government, and we are working with the minister and department as options are evaluated and decided upon.
"We welcome the support of the minister and the department in this process.
"Consideration of sale of non-core assets has been an ongoing part of both this process, and of the wider efforts to ensure the financial sustainability of the group."