Delta denies customer refund backlog after company tweeted it was 'months' behind

As the Department of Transportation increases its call on airlines to promptly refund passengers, Delta Air Lines is telling some people on social media that it could be months before they see their money returned.

Still, the company insisted to ABC News that it was working "in a timely fashion."

DOT requires airlines to refund passengers within seven business days if the customer paid by credit card -- or within 20 days if they paid with cash or check. Transportation Secretary Pete Buttigieg recently warned Southwest Airlines, after its holiday season meltdown, that his agency "will use the full extent of its investigation and enforcement authority to ensure Southwest complies with its refund obligations."

On Sunday, Delta tweeted that it was "months behind" on processing some refunds for canceled flights.

In one response to a user who asked for an update on the status of what they said was a refund request of more than $13,000, a Delta representative tweeted back: "Due to the backlog/ high volume of refunds, the Refund Department is a couple months behind on processing."

The carrier also tweeted in July and in November that refunds were backlogged, asking customers to allow more than a month for a response.

But Delta this week denied the existence of a backlog in refund requests. In a statement to ABC, the airline said, "As always, we will provide refunds to eligible requesting customers who elect not to travel as the result of a significant delay or cancellation and seek to do so in a timely fashion."

Although the tweets were sent from the Delta Twitter account and remain posted, it's unclear if there are delays in customers receiving refunds.

Last year, DOT levied more than $7.25 million in fines against six airlines, including U.S. carrier Frontier, for not providing prompt refunds.

The department has said it would hold all airlines accountable "if there is evidence that they are failing to meet their refund or reimbursement obligations."