LONDON (Reuters) – A website for essential workers in Britain applying to get a test for COVID-19 said on Friday it was closed because of high demand just hours after the government increased the number of people eligible for its testing programme.

Health minister Matt Hancock said Friday’s launch of the new online booking system to an increased number of essential workers, such as teachers and delivery drivers, was part of efforts to boost Britain’s testing programme to reach his target of 100,000 tests a day by the end of the month.

The government has been criticised by some health workers and scientists for failing to move quickly enough to increase its testing programme, with some essential workers staying at home with symptoms similar to those of COVID-19.

“There has been significant demand for booking tests today. We apologise for any inconvenience. We are continuing to rapidly increase availability. More tests will be available tomorrow,” the health ministry said on Twitter.

A spokesman for Prime Minister Boris Johnson said the system, which offers home-testing kits and appointments at drive-through testing sites, had quickly run out of available slots. He said all Friday’s available 5,000 home-testing kits and 15,000 testing slots at drive-through sites had been booked.

“The reason the website stopped taking bookings was because all of the available slots had gone. It’ll be back up and running when the next batch of slots are available for each given day,” the spokesman told reporters.

An existing system for employers of the National Health Service to book tests for workers and tests done in hospitals or other clinical settings would continue alongside the new programme, he said.

Some 23,560 tests were carried out on April 22 – the latest day for which data is publicly available, and Britain now has a testing capacity of just over 51,000.

(Reporting by Elizabeth Piper; Editing by Alistair Smout and Stephen Addison)