The British government says it is investing in a coronavirus test that gives results in as little as 20 minutes, as critics say tests for the virus are being rationed because the system can’t cope with demand.

Health Secretary Matt Hancock says the government is expanding trials of two new tests — a no-swab saliva test and another that gives results in minutes. It’s also running a trial on the benefits of repeat testing of people without symptoms.

Britain has hugely expanded its testing capacity since the start of the pandemic, but critics say it is still not doing enough to find and isolate people with the coronavirus.

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Anyone with symptoms is eligible for a test, but the BBC reported Thursday that people who enter their postcode into the government’s website are sometimes being directed to drive-through centers hundreds of miles away.

Hancock insisted the system was working well despite some “operational challenges.”

The government says it has the capacity to perform almost 350,000 tests a day, though only abut 180,000 are actually being processed daily.