The district council has said what it thinks a deep hole complete with rusty steps which emerged on a front lawn could be.
They believe it could be a sewer.
The hole, which measures around two feet by two feet, appeared when Emma James was mowing the grass at her home in Kynaston Avenue, Stoke Mandeville.
Since the Bucks Herald first broke the story there has been widespread media interest in the mystery hole.
Aylesbury Vale District Council has now looked into the history of the property and believes it could be a sewer.
In an email it told householder Kevin James that responsibility for it now falls to Thames Water.
He added: “They have no record of these sewers on their mapping system as they were never mapped by them but this does not stop them being their responsibility.
“The fact that water is rising in the chamber suggests that the surface water from the houses is having difficulty percolating through the soil and debris that has fallen into the chamber and is not running smoothly into the main sewer.”
Thames Water are sending out an engineer today (Wednesday) to investigate further.
Councillor Marcus Rogers, who has been helping the couple, said he would expect them to pump it out, ensure it is working correctly and position a manhole cover over the hole to enable future access.