A Taiwanese airline has apologised for requesting paperwork from an employee after her death, in the latest development of a case that has sparked widespread anger.

The 34-year-old Eva Air flight attendant, surnamed Sun, died earlier this month after reportedly feeling unwell during a flight.

Days after her death, the airline texted her asking for proof that she had applied for leave during the time she was in the hospital.

Ms. Sun's death has enraged many online amid speculation that she was overworked. Taiwanese authorities and Eva Air are now investigating whether Ms. Sun was denied medical help or discouraged from taking sick leave.

In a statement provided to the BBC, Eva Air said that it had maintained contact with her family when she was in hospital and was "deeply saddened" by Sun's death.

"The health and safety of our employees and passengers are our highest priorities," the airline said, adding it was "conducting a thorough review" of the case.

Ms. Sun reportedly felt ill on 24 September during a flight from Milan to Eva Air's base in Taoyuan City in Taiwan. She was hospitalised upon arrival and eventually died on 8 October.

Anonymous social media users claiming to be her colleagues have alleged Ms. Sun was pushed to continue working even when she felt unwell.

The China Medical University Hospital in Taichung, where she died, has not officially disclosed the cause of her death.

Flight records in the last six months showed that Ms. Sun had flown an average of 75 hours per month, which is within regulatory limits, Taiwan's Central News Agency (CNA) reported. She joined the airline in 2016.

According to Ms. Sun's family, days after her death, her phone received a text message from an Eva Air representative asking for documents proving that Ms. Sun had applied for leave in late September, which was the period she was in the hospital.

The representative asked her to send in a picture of the leave documents. The family replied to the text with a copy of Ms. Sun's death certificate.

Senior Eva Air officials said the text was a "mistake by an internal employee."

They told a press conference that they had personally apologised to Ms. Sun's family for the error.

"The departure of Ms. Sun is the pain in our hearts forever," Eva Air President Sun Chia-Ming said.

"We will carry out the investigation [into her death] with the most responsible attitude."

Since 2013, Eva Air has been fined seven times, mostly for offences related to staff working overtime, CNA said.