Egypt has asked for proof from a French warship, on its way to a breaker's yard in India, that it is not carrying toxic waste breaching the Basel Convention.
French warship, Clemenceau is due to reach India in March
Officials have said that the ship, Clemenceau, will be barred access to the Suez Canal and turned back if the required papers are not provided.
France says it is providing the information asked.
Earlier, two Greenpeace activists boarded the warship to protest against its journey to India.
Greenpeace says India is not equipped to deal with the asbestos-lined warship's toxic waste.
The Clemenceau is expected to arrive in India in early March.
The national co-ordinator of Egypt's environmental affairs agency, Cpt Mahmoud Ismail, said in a statement that written proof was needed from both France and India showing that the ship was not carrying hazardous waste in breach of the Basel Convention.
The ship is supposed to contain high levels of asbestos
The Basel Convention is an international treaty which prevents trade in hazardous materials.
The French defence ministry has denied that the ship has been officially refused access by Egypt, but added that it had been asked for more information.
"We are being asked for extra technical information, which we are in the process of providing," defence spokesman Jean-Francois told the AFP news agency.
"We have not been notified of a refusal decision at this point."
Earlier, two Greenpeace activists approached the ship in a motorised dinghy and have chained themselves to the mast, the French defence ministry said.
"We let them board. In no way are they impeding the Clemenceau's journey," said a spokesman.
Stay away from India
The carrier left the French port of Toulon on 31 December after a long legal battle.
A monitoring committee of India's Supreme Court ruled last week that the information about the vessel was inadequate and asked the carrier to stay 200 nautical miles away from Indian waters pending a final decision.
The court also said that allowing the ship into Indian waters would break the Basel Convention.
The company in India which has been given the contract of breaking the Clemenceau says its workers will be adequately protected when working on the asbestos-lined warship.