Firefighters took six hours to put out a massive blaze that engulfed a building containing recycled oil and solvents in Tuas early yesterday.

The fire affected an area about the size of a football field. The flames were also rapidly spreading along nearby drains, said the Singapore Civil Defence Force (SCDF).

No one was reported to have been injured.

The SCDF said it was alerted to the incident at 48 Tuas Crescent - where Unifine Star Petrochemical is located - at 6am and deployed 34 emergency vehicles and 130 firefighters.

Firefighters arrived on the scene within four minutes of the call, an SCDF officer told reporters after the fire was under control.

Unifine Star collects, disposes of and recycles toxic industrial waste.

In Facebook posts, SCDF said during operations, there were "multiple explosions" from metal drums that stored flammable industrial liquids.

An SCDF officer later said a "two-pronged attack" was mounted to stop the "running flow fire" spreading downstream in the drains and to suppress the blaze in the building, so that the surrounding infrastructure would not be affected.

Due to the intensity of the fire, firefighters first used 10 water jets and three unmanned firefighting machines to douse the flames, before SCDF personnel donned breathing apparatus and face masks to enter the premises.

An unmanned aerial vehicle was flown over the site to monitor the situation from the air, while foam was used to cover the surface of flammable liquids.

When asked by reporters whether the toxic industrial waste that Unifine Star stored on site could lead to pollution, the SCDF officer said an SCDF hazardous materials (hazmat) vehicle was deployed to roam and collect samples near the scene so that they could be sent to the National Environment Agency (NEA) for checks.

NEA said it also sent its officers to Tuas to measure the area's air quality, which remained within safe limits. Readings recorded at the volatile organic compound monitoring station in Tuas were also at safe levels and special measures were not needed.

National water agency PUB told The Straits Times that water quality in reservoirs has not been affected as the drains near the site of the fire discharge water into the sea via the Tuas basin.

Both PUB and NEA are continuing to monitor the situation, including the water quality of the discharge into the surrounding waters off Tuas.

SCDF is investigating the cause of the fire.