Angel Aparicio, who is in charge of the government department overseeing the project, said the study had unearthed significant problems that would make digging the tunnel between Spain and Morocco a challenge, the BBC reported Saturday.

"The material here is not compact enough to allow an initial excavation," Aparicio said of the proposed tunnel under the Mediterranean Ocean.

"It is clay with rock and so it is not as compact as it is in the rest. As we have a lot of water we have a very high pressure and we are not sure whether we could go through with the tunneling," he added.

Both the Spanish and Moroccan governments support the tunnel as a potential transport hub between the two countries, but it is expected to cost at least $8 billion.

The BBC said if Spain does decide to move forward with the tunnel project, it is expected to take 15 years to complete.