As Thomas Cook customers anxiously wait to see if and how their holidays might be affected, some say they have already found themselves in "horrible" situations abroad.
The travel company is requesting £200m in extra funds from the government in order to stay afloat, and Foreign Secretary Dominic Raab has said affected holidaymakers could be flown home if the firm collapses.
Customers at a hotel in Tunisia say they were prevented from leaving the property on Saturday unless they paid extra fees - thousands of pounds in some cases - to cover what the resort says it is owed by the tour operator.
"We're being held hostage," said Ryan Farmer, from Leicestershire, one of those staying at Les Orangers resort in Hammamet, near Tunis.
He told BBC Radio 5 Live the hotel asked everyone who was due to leave that day to come to reception, where they were asked to pay "additional fees, obviously because of the situation with Thomas Cook".
"We've been up to the gates, they had four security guards on the gates, holding the gates closed, and were not allowing anybody to leave," he added.
Mr Farmer, who described the mood at the hotel as "horrible", said an elderly lady who had already paid for her holiday in full was made to pay an additional fee of over £2,000.
Although the gates of the hotel have since been opened, one customer told the BBC they feared they may be closed again when the next group of guests was due to leave.
The guests say they have been told not to pay the hotel by their Thomas Cook representative - and that the British Embassy later became "involved" and had spoken to the hotel.
No official statement has been released by Thomas Cook, but the company is telling customers via Twitter that it is aware some guests were asked to pay extra fees, adding: "We have refunded those customers who paid on their credit cards."
The company has not commented on potentially refunding customers who may have paid through other methods.
Chris Rutherford, from Southampton, who is staying at Les Orangers resort, spoke of a similar experience.
"The hotel reception told us we need to pay £4,000 to be allowed to leave," he said.
"They made an elderly lady who had fallen and broken her arm whilst on holiday pay £2,500 to leave the hotel...
"The Thomas Cook rep told us last night they were only dealing with people who had to leave that evening, as we are supposed to be here until Friday we got no information and have not had any further correspondence with Thomas Cook."
Gary Seale, who is also at the resort, said he was hoping to catch a flight back to Manchester - but refused to pay the additional fees and was not allowed to leave.
"It's been very fraught but it hasn't got to fisticuffs yet," he said.
But he added that more customers are due to leave on Monday and it could be "carnage if this isn't sorted".
Fatima De Andrade is staying at the hotel with her boyfriend, and described the scene near reception on Saturday night as "absolute madness".
"Myself and my boyfriend went out for a day trip and when we arrived back to the hotel around 6pm we saw the lobby full of people some crying and were completely clueless."
She said people's suitcases were "everywhere" and people were panicking.
'People were furious'
She added: "The wi-fi was turned off, to which management said it's due to the weather it's not working, so we couldn't check what was happening online contact family back home."
Ms De Andrade said notes were put through room doors demanding payment.
"People were furious," she said.
"Guest who had their flight were walking up to the gate with their suitcases to leave and security weren't letting them, some tried to jump the wall and security grabbed them back."
Ms De Andrade added: "Myself and my boyfriend feel safe however it's not knowing what management will do when it's our turn to check out."
The BBC has contacted both Les Orangers resort and the British embassy in Tunisia but has not yet received a response from either.