SAO PAULO, May 10 (Reuters) - Brazilian steelmaker and miner CSN posted a 479.7 million real ($93.3 million) first-quarter net loss late on Thursday, hit by lower iron ore and steel prices.

The loss was almost 42% smaller than a year earlier, but that was largely down to tax gains.

Net revenue was down 14.2% at 9.71 billion reais in the three months to March 31 as the lower prices offset steel and iron ore sales volumes that rose by 5% and 6% respectively.

Adjusted earnings before interest, taxes, depreciation and amortization (EBITDA) came in at 1.97 billion reais, down 39% from a year earlier, with the adjusted EBITDA margin falling 8 percentage points to 19.3%.

"It is already possible to see a more positive dynamic for the next results, with an acceleration in demand and a recovery in price, especially in the mining segment," the company said.

CSN added that its weaker operational performance also weighed on its financial leverage, a key focus of the company, with the net debt to adjusted EBITDA ratio rising to 3.13 from 2.58 in December and 2.45 a year earlier. ($1 = 5.1420 reais) (Reporting by Andre Romani Editing by Mark Potter and David Goodman)