A Taiwanese airline has apologised for requesting paperwork from a dead employee, 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. 

Many online have speculated she was overworked.

Taiwanese authorities and Eva Air are investigating her death, focusing on whether she was denied medical help or discouraged from taking sick leave.

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 hospital.

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

Senior officials of the company told a press conference on Friday that the text was "a mistake by an internal employee" and that they have personally apologised to Ms Sun's family for the error.

At the press conference on Friday, EVA Air President Sun Chia-Ming said "the departure of Ms Sun is the pain in our hearts forever."

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

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