Qantas is looking into whether a laboratory that tested passengers for a repatriation flight from India had its accreditation suspended last month.

The website of India’s National Accreditation Board for Testing and Calibration Laboratories shows New Delhi-based CRL Diagnostics was suspended on April 6.

According to the ABC, the laboratory was used to COVID-19 test “vulnerable” Australians who had been in pre-flight hotel quarantine, detecting 46 positive cases and an additional 24 close contacts.

All were stopped from boarding the flight, which landed in Darwin on Saturday with just 80 people on board.

At least three of the people who could not travel after testing positive to the virus had since returned negative results, the ABC reported.

Qantas is now reviewing whether the diagnostic agency used the lab for the pre-departure test.

“We have reiterated to our diagnostic agency that they must ensure that any laboratory they use has all current and appropriate accreditations,” a spokeswoman said on Sunday.

She said the airline continued to work with the Department of Foreign Affairs and Trade to ensure the process was “working as it should”.

“The reason we went to India was to bring home as many Australians as possible,” the spokeswoman said.

“Together with DFAT, all the protocols put in place were designed to minimise the risk of importing the virus and maximise the safety of everyone on board.”

Prime Minister Scott Morrison said protecting Australians required being cautious.

“We will work closely with Qantas … they will get every support from us but it is a very difficult environment to operate in at the moment,” Mr Morrison told reporters.

CRL Diagnostics is among a list of 44 labs suspended in India.

The board told the ABC the lab was suspended for noncompliance with accreditation norms, while CRL Diagnostics reportedly said it was for misusing the board’s logo.

Australia was among dozens of countries to temporarily ban all travel from COVID-ravaged India, where more than 24.3 million cases and 266,207 deaths have been recorded, according to the Johns Hopkins Coronavirus Resource Centre.

The returned travellers are being quarantining at the Howard Springs facility in Darwin.

More than 9000 people had registered to return to Australia from India last month.