Blackpool boss Lee Clark has signed Manchester United midfielder Joe Rothwell on loan until the end of the season.
Hearts have been hit with an indefinite transfer embargo over a failure to make payments to players.
The Scottish Premier League has announced Hearts have "not paid a number of bonuses and appearance payments" and also face a disciplinary hearing, with a full range of sanctions at the SPL's disposal.
Hearts insisted bonus payments from the William Hill Scottish Cup final win over Hibernian on May 19 had been paid.
However, it is understood bonuses had not been received last week, so the payments were likely included in this month's pay packet, on December 16 - six months late.
Payments of bonuses due this season - such as a goalscoring or clean-sheet fee - are understood to be in arrears, amounting to a six-figure sum.
A statement from the SPL read: "As a result, and as described in SPL Rule A6.23, Heart of Midlothian is subject to an embargo on the registration of players until such time as the SPL board is satisfied that the remuneration default no longer continues."
The rules Hearts have been cited for relate to failure to pay players and club officials and were brought in during the summer following a series of late payments by the Edinburgh club last season. Hearts acknowledged the SPL's statement and are taking legal advice.
A notice on the club's official Twitter page read: "All Scottish Cup Final bonuses have been paid."
A statement on the club website read: "Heart of Midlothian today received notification from the SPL of an embargo on the registration of players in relation to an alleged remuneration default. "The club is consulting with its legal advisors and will make no further comment at this time."
Hearts were initially placed under a 60-day transfer embargo on October 24 for failing to pay their players and some staff their monthly wages on time for two consecutive months. That sanction was due to end on December 23.
Hearts face a myriad of financial difficulties and players voluntarily deferred their wages last month but they were paid before receiving their full salary for this month on December 16.
The news came on a day Hearts announced over £1million has been raised through a share issue scheme which was launched in late October to raise £1.79m.
Four thousand supporters signed up to the scheme, Hearts said, but there remains a shortfall of almost £800,000 between now and the end of the season, leaving the club in a precarious position.
Hearts, at the request of supporters, will continue to accept completed applications and payment up until the conclusion of Sunday's Clydesdale Bank Premier League match at home to Dundee United and say the figure of £1.05m raised - through the share issue scheme and other fundraising - may rise.
Seven days before the deadline - the most recent update - Hearts revealed more than £800,000 had been raised and urged fans to sign up or that the club could face another do-or-die situation after averting a winding-up order earlier this month by paying a £450,000 tax bill.
Hearts settled another issue with Her Majesty's Revenue and Customs by agreeing to pay £1.5million over three years.
Supporters have been urged to continue to attend matches in high numbers in a bid to reduce the shortfall after £161,000 was raised in "unbudgeted" ticket sales from the matches at home to St Mirren, Celtic and Aberdeen. Hearts director Sergejus Fedotovas said fans had "given the club a lifeline in its darkest hours".
Fedotovas, right-hand man to majority shareholder Vladimir Romanov, said on the club's official website: "The best way that we can all push through this difficult situation is by supporting the team and buying half season tickets and match tickets. "Together we can emerge a leaner, stronger football club and I expect that the supporters will be the ultimate beneficiaries as we progress towards making Hearts a club that is one of the most progressive and supporter-centric in the country."
When the share issue scheme was launched the prospect of supporter ownership was mooted. Discussions with Supporters Direct Scotland are continuing, Fedotovas added.
"We are now working on the most suitable model that will give the club the best long-term chance of development under true supporter control," he added.
"We expect to announce further details of this in the early part of 2013."
Hearts manager John McGlynn has consistently bemoaned his lack of attacking options and Lithuanian striker Arturas Rimkevicius arrived in Edinburgh last week on trial.
It appears, for now, a possible deal is off.