(Adds comment from conference call, debt figure)
MEXICO CITY, March 30 (Reuters) - Mexico's ICA posted a fourth-quarter net loss more than five times higher than in the same period a year earlier, as the embattled construction company won fewer contracts and its debt soared.
ICA, which has not posted a quarterly profit since 2013, on Wednesday said it lost 10.591 billion pesos ($615 million) in the October to December period, compared to 2.082 billion pesos a year earlier.
Revenue halved in the quarter compared to a year ago, while the cost of sales rose more than 70 percent, pushing it to an operating loss.
The former industry leader has defaulted on about $60 million of interest payments since December, replaced its chief executive and hired investment bank Rothschild to come up with a debt restructuring plan by March.
But the restructuring plan is still underway, CFO Pablo Garcia said in a brief conference call. Executives did not accept questions.
In its results statement, the company said it has fired more than half its workforce since the end of 2014 and cut costs by 46 percent.
ICA has failed to win new construction contracts to service its debt, which rose sharply after a drop in the value of Mexico's peso against the dollar.
However, it did manage to secure a new loan in February to finish one of its larger highway projects.
The company said the fall in profit was due to weaker construction revenues, the exchange rate and restructuring provisions on certain projects.
By the end of 2015, total consolidated debt had risen to 67.6 billion pesos, 7 percent higher than a year earlier.
The company's creditors have been seizing ICA's shares in airport operator OMA as collateral on loans that came due after the default.
That helped lower total debt to 62.313 billion Mexican pesos by the end of this month.
The company has also prepared a bankruptcy protection filing as a precaution, Reuters reported.
ICA said it is now focusing its efforts on defining a restructuring plan.
$1 = 17.212 pesos at end-December Reporting by Christine Murray, Gabriela Lopez and Alexandra Alper; Editing by W Simon and James Dalgleish