Madurai Collector T.G. Vinay on Sunday said testing had been stepped up since details of samples collected in each district — as on June 7 — were made public by the State government in a bulletin the same day.

Mr. Vinay said 4,556 samples had been taken since then, taking the total count to 20,776.

The State bulletin put the total number of tests conducted in Madurai district, as on June 7, at 14,102 . “But the actual number was 16,220 samples,” the Collector said.

Individual labs, approved by Indian Council for Medical Research to update the numbers on its portal, did not do so with regard to the district’s figures, he pointed out.

A Public Health Department source said at least 500 samples were tested daily over the last week. On June 12 and 13, over 900 tests were conducted.

“There has been a steady increase in the collection of samples because of the inflow of returnees. We have stationed mobile health units on Soorapatti, Vadipatti and Madurai-Natham highway to test persons travelling by cars. Those who are travelling to Madurai by train from Villupuram can also be tested at Madurai junction. Regular checks at the airport are taking place too,” the source said.

Within the Corporation limits, anyone with symptoms of influenza were being tested at fever clinics. Testing had been stepped up at primary health centres.

A revenue official said there were at least 2,000 cars and minivans carrying hundreds of people into the district. “Although the ideal move will be to test every single vehicle, health workers are testing only those who have symptoms, especially cough, cold or fever. The symptoms need to be pronounced to get a test.”

The Collector, however, said the administration would continue to ensure a steady increase in the number of tests of people at the district border.