Thick plumes of smoke were seen rising from Tanjong Kling in Jurong after NSL OilChem, which deals with oil and chemical waste, caught fire on Tuesday (Mar 21).
Channel NewsAsia reader Diana Lynn Diaz Nasol said her colleague saw the smoke from their office beside the burning building at around 12.15pm.
Singapore Civil Defence Force (SCDF) firefighters arrived about five minutes later, and her office and another office adjacent to the site were evacuated, she said.
Ms Diana said she heard "many explosions". Police instructed onlookers to move away from the scene, she added.
SCDF said in a Facebook update at 1.14pm that it was alerted to the fire at 23 Tanjong Kling Road and that firefighters were at the scene with water jets.
SGSecure mobile app users and StarHub mobile subscribers within the immediate vicinity of the fire incident would have received an advisory message urging the public to stay away from the area, it added.
Last month, a huge fire broke out at Eco Special Waste Management in Tuas. The fire took 200 SCDF firefighters four hours to put out.