Mr Hampton has photographed planes all over the world, his mother said
The Foreign Office has said it is now unsure when two British plane-spotters arrested in India could be released.
Stephen Hampton and Steven Ayres, from Bristol, were arrested on Monday on suspicion of monitoring flights at Delhi International Airport.
A Foreign and Commonwealth Office (FCO) spokeswoman said they were still being held at a New Delhi immigration centre.
The FCO had said previously that the two men had been, or were due to be, released.
The spokeswoman said the two men were being held while the Indian authorities continue to investigate the matter.
"The FCO cannot interfere in an ongoing police investigation nor can we secure their release," she said.
"The British High Commission has raised the case with the Indian authorities though we are restricted in the representations we can make as we cannot interfere in the Indian judicial system."
The spokeswoman said consular staff had been in regular contact with both men and continued to provide consular assistance.
"We are also in touch with the next-of-kin in the UK and keeping them informed of developments," she added.
On Saturday the FCO initially issued a statement saying the men had been released and later changed this to say they were waiting to be informed of their release by the Indian authorities.
The spokeswoman said this information was now known to be incorrect.
Mr Hampton, a railway worker from Keynsham, and Mr Ayres, from St George, sparked suspicion after asking a Delhi hotel for a room overlooking a runway.
They were carrying an air traffic control scanner, laptop, binoculars and cameras.
Mr Hampton's mother Eileen Cock said he had travelled all over the world photographing aircraft.
Dan Norris, MP for Wansdyke, has been liaising with the FCO to try to bring them home.