Reading fans have called for an explanation of the delay in the full takeover of the club by majority shareholder Anton Zingarevich.
Russian businessman Zingarevich bought 51% of the club 16 months ago.
He was due to purchase the remaining 49% from previous owner Sir John Madejski by the end of September,
but that deadline has now passed.
"We want some transparency," said Supporters' Trust at Reading (STAR) vice-chairman Richard Langley.
"We want to know what it going on with the football club."
Newspaper reports at the weekend
suggested Zingarevich was looking to sell his 51% stake
and STAR fears the club could go the same way as Portsmouth - who suffered years of financial misery at the hands of previous owners.
"We, as an organisation, are awaiting responses from the club with regards to some of our questions," added Langley to
BBC Radio Berkshire.
"We want to know it's not going to turn into another Portsmouth and the club is secure for another 20 years.
"The appetite is still for Anton to keep going and take the controlling stake and set Reading up for the future. There was a great buzz when he came in and I hope this is just a little hiccup in the process in him securing the rest of the shares.
"The hope among all Reading fans is Anton Zingarevich will buy the remaining 49% of the shares and the future of Reading is not muddied and we know who owns the football club."
Since the Russian became involved with the club in January 2012,
Reading have been promoted to the Premier League,
relegated back to the Championship
and have also changed their manager.
"The lack of funds Nigel Adkins has had in the transfer market has maybe led to Reading fans putting two and two together and getting five.
"But why wouldn't the football club reassure fans? If there is nothing to worry about why doesn't somebody come out and say it's just one of these things, it will happen in time there is no problem here and no hiccup."
Promotion to the top flight in 2012 earned the Royals an estimated £90m, with half that money coming from television-related revenue.
However, the club were relatively frugal when strengthening the squad for the Premier League.
In total, they spent less than £10m in attempting to cement their status, with the £2.4m purchase of Adrian Mariappa from Watford their biggest outlay.
Relegation last season meant the club missed out on the new £5bn global television deal, which would have earned them upwards of £100m, but Reading will still receive in excess of £60m over a four-year period in parachute payments.
The club have also spent little this summer, bringing in Royston Drenthe, Wayne Bridge and Danny Williams, while receiving over £4m for the sales of Mariappa and Jimmy Kebe to Crystal Palace.
Madejski owned Reading for 22 years before agreeing to sell a controlling interest to Thames Sports Investment, led by Zingarevich, in January 2012.
The deal to acquire the 51% stake, thought to be worth about £40m, with a bonus to Madejski for promotion to the Premier League, was expected to be completed in March, but was delayed by three months.
The deal for acquiring the remaining 49% is believed to be worth £25m.
Thames Sports Investment and Reading FC have been unavailable for comment.