Originally Published: 16 FEB 23 11:36 ET

By Alicia Wallace, CNN

(CNN) -- Americans continued to add to their debt at the end of last year — and grew their credit card balances at record rates, according to data released Thursday by the Federal Reserve Bank of New York.

Total US household debt hit $16.9 trillion during the fourth quarter, an increase of $394 billion, or 2.4%, from the prior three-month period, according to the Fed's latest Quarterly Report on Household Debt and Credit. While the lion's share of the debt is attributable to mortgages, the report showed that not only are credit card balances swelling at record levels, delinquencies are on the rise as well.

Credit card balances increased nearly 6.6% to $986 billion during the quarter, the highest quarterly growth on record, according to New York Fed data that goes back to 1999.

And as debt is growing, Americans are having more trouble meeting payment obligations: The share of current debt becoming delinquent increased across nearly all debt types, with credit cards and auto loans showing delinquency transparency rates of 0.6 and 0.4 percentage points, respectively.

While total delinquency levels remain below what was seen pre-pandemic — 2.5% of outstanding debt was in some stage of delinquency as of December versus 4.7% at the end of 2019 — the fact that delinquency rates are escalating in spite of a strong labor market environment is concerning, New York Fed researchers said.

"Although historically low unemployment has kept consumers' financial footing generally strong, stubbornly high prices and climbing interest rates may be testing some borrowers' ability to repay their debts," Wilbert van der Klaauw, economic research adviser at the New York Fed, said in a statement.

This story is developing and will be updated.