A new, high-speed coronavirus test has been granted emergency clearance by the Food and Drug Administration, the latest effort to expand capacity to diagnose the fast-spreading pathogen.

The test was developed by diagnostics giant Roche Holding AG and is designed to run on the company's automated machines, which are already installed in more than 100 laboratories across the U.S.

It is only the third coronavirus diagnostic to receive emergency-use authorization from the FDA, following a test developed by the Centers for Disease Control and Prevention and one from the New York State Department of Health.

The FDA has been working to ramp up the speed and quality of coronavirus testing after a slow and troubled start in the U.S. Until two weeks ago, only the CDC was authorized to conduct tests, some of which turned out to be inaccurate. The CDC says it has since remedied those issues.

Since then, the FDA has given permission to hundreds of U.S. academic hospital labs to immediately begin using their own tests for the new coronavirus without first obtaining emergency authorization. The labs are supposed to follow certain steps to validate their own tests, and to ultimately seek FDA authorization.

Currently, all testing is based on identifying unique portions of the new coronavirus's genetic sequence. But Roche's tests can be conducted faster than manual laboratory tests. Its machines provide results in three and a half hours and can run many tests in parallel -- though as they are located in laboratories, it will take additional time for samples to be sent for testing. Its most advanced machine can process around 4,128 samples every 24 hours.

So far, over 13,000 patient specimens have been tested by CDC and state public-health labs in the U.S., according to figures CDC posted online.

While capacity has increased, the rollout has been in a patchwork fashion that still isn't meeting demand for tests.

The spotty rollout of testing in the U.S. has become a contentious political issue, with members of Congress criticizing the Trump administration for not having better testing capacity. The Trump administration has said that sufficient test kits are available.

An "emergency team" of Roche scientists started work on a new test as soon as China shared the genetic sequence of the virus in January. It normally takes years for a new test to be developed and approved, according to Roche Diagnostics Chief Executive Thomas Schinecker.

The company has also been working closely with the CDC in the past few weeks to install more machines across the U.S., said Mr. Schinecker.

Other diagnostic equipment makers also have been developing new coronavirus tests, including Qiagen NV, BioMerieux and Abbott Laboratories. Some hospital systems in the U.S. have developed their own tests, which will have to seek FDA approval.

Write to Denise Roland at Denise.Roland@wsj.com and Peter Loftus at peter.loftus@wsj.com