Madam Mariam Atom was headed to work at KK Women's and Children's Hospital (KKH) early yesterday morning, but she never got to her destination.

The 70-year-old cleaner died after being trapped under a bus in an accident at the junction of Ang Mo Kio Avenue 8 and Avenue 3. She had to be extricated from under the bus by firemen and was pronounced dead at about 6.40am.

The 65-year-old male bus driver was arrested for causing death by a negligent act, the police said.

Madam Mariam, an Ang Mo Kio resident, was on her way to KKH, taking the same route she had used every day for about 10 years, her relative Nur Hidayah Abd Samat, 31, told The Sunday Times.

"She is my mother-in-law's auntie, and they were very close. My mother-in-law was her shopping buddy," Ms Hidayah said.

Madam Mariam leaves behind a husband and son, and four grandchildren.

"She said that as long as she was healthy, she would work," Ms Hidayah said, declining to comment on how the accident happened as police investigations are ongoing. "She was a very bubbly person, and also very kind-hearted," she added.

SMRT vice-president for corporate communications Patrick Nathan told The Sunday Times: "Our care team is doing its best to reach out to the family to provide necessary support during this difficult time. We are extending our full cooperation to the police for investigations into the accident."