There was speculation over the future of the investigation when it emerged that funding would run out at the end of September.
But the Home Office has now confirmed that it is considering an application from the force for more cash.
In a blog published on Wednesday, it said: “We have received and are considering a request from the Metropolitan Police Service to extend funding for Operation Grange until the end of March 2019.
“The Home Office maintains an ongoing dialogue with the MPS regarding funding for Operation Grange.”
Madeleine was three when she was last seen on holiday with her parents in Praia da Luz in Portugal in May 2007.
Scotland Yard launched its own investigation, Operation Grange, into her disappearance in 2013 after a Portuguese inquiry failed to make any headway.
UK detectives were granted an extra £150,000 in March to continue the probe, to cover until the end of September.
Operation Grange has cost £11.6 million so far.
The appeal for more funds comes after Kate and Gerry McCann had to shut down the online store on their Find Madeleine website.
Mrs McCann put up a message on the website saying: “Unfortunately due to many commitments and pressures, I am unable at this time to attend to website orders.
“Your support means a lot to us. Your kindness and generosity is no less appreciated however and continues to buoy us up. Thank you again – Kate.”
Donations to the fund can still be made on the website, she added.