NEA said it will be taking legal action against Rynamo Building Services under the Environmental Protection and Management Act.
The PUB had detected blue discharge in a drain. Investigations found that the discharge came from a paint drum that had tipped over into the drain at Mayfair Industrial Building at 51 Jalan Pemimpin.
In a statement on Friday night, the PUB said it contained the discharge within the drain, which was cleared up on the same day.
Water samples taken downstream of Clover Way yesterday showed that the quality of the water was not affected, said PUB. It added that it has a "comprehensive system" to monitor the quality of the raw water in reservoirs.
The raw water is treated at the waterworks according to World Health Organisation drinking water quality guidelines before it is supplied to households, PUB said. Both agencies said they take a serious view towards pollution of Singapore's waterways.
The public can contact NEA at 1800-2255 632 or PUB at 1800-284 6600 if they spot any suspected pollution.