A maid suffered a 90-minute ordeal when she got stuck in a Housing Board lift which suddenly shot up 17 floors before trapping her inside.

Ms Evi Lisnawati, 36, was on her way to pick up her employer's children from a tuition centre when she entered the lift on the fifth floor of Block 317 in Ang Mo Kio Street 31 at about 7.15pm on Monday.

When it got to the ground floor, the lift door opened just 20cm, then closed again. She pressed the "door open" button repeatedly, but to no avail and the lift then went up to the third floor and stopped.

After pressing the button a few more times, the lift began moving again. But instead of going down, this time it went up to the 20th floor "very fast". Ms Evi, who is from Indonesia, said she fell and hit her back on the walls and lift floor.

She heard a "bump", then the lift descended and ended up stuck between the 19th and 20th floors.

"People on the 19th floor could only see my legs," she said. She then called her employer to tell her what happened.

Personnel from the Essential Maintenance Services Unit came around 7.30pm but could not open the door.

The Singapore Civil Defence Force (SCDF) was alerted to the incident at about 8.30pm and the rescuers freed Ms Evi with the help of a lift technician within half an hour.

She was assessed by paramedics, but declined to go to hospital. "I can just rest at home and take some medicine," she said.

It was a traumatic experience for Ms Evi, who said she could not sleep until 1am yesterday. Although her employer asked her to rest, she insisted on cooking dinner.

The Ang Mo Kio Town Council said it is investigating the incident at the 22-year-old block.

On Oct 9 last year, Madam Khoo Bee Hua, 85, had her left hand severed by the doors of a lift in Block 322, Tah Ching Road. In another incident in January, a faulty HDB lift in Punggol's Edgefield Plains was suspended from operation after one of the lift's inner doors stayed opened as the lift moved.