(Reuters) - U.S. rare earths producer MP Materials ( MP ) said on Thursday that it swung to a first-quarter loss due in part to rising production costs and interest expenses, though results met investors' expectations.

The results are the first since the Las Vegas-based company said last month it would stop shipping the critical minerals to China for processing in response to Beijing's tariffs.

The move essentially halts a major source of revenue for the company, although its impact will not reflect until second-quarter results, expected in August.

For the first quarter ended March 31, the company posted a net loss of $22.6 million, or 14 cents per share, compared to net income of $16.5 million in the year-ago period.

Excluding one-time items, the company lost 12 cents per share, matching analysts' expectations, according to IBES data from LSEG.

Shares of the Las Vegas-based company fell 1.3% in after-hours trading.

MP said its cost of sales, excluding depreciation and related items, increased by roughly $13.3 million, due in part higher production costs associated with the low utilization of its refining facilities. The company is increasing the use of those facilities.

MP's interest costs also rose by nearly $5 million due in part to rising expenses tied to a convertible note due in 2030.

MP produces rare earths concentrate at its California mine that it had sold to refiners in China, until last month, and elsewhere. It also refines rare earths in California.

The company produced 12,213 metric tons of that concentrate during the quarter, 10% higher than the year-ago period.

At its California refinery, MP produced 563 metric tons of neodymium and praseodymium (NdPr) - the two most in-demand rare earths - during the quarter, more than four times the year-ago period.

Realized prices of rare earth concentrates during the quarter rose 12% from the year-ago period, though prices for NdPr fell 16%.