It said the asphalt plant, Blacktop Industries Sdn Bhd, is expected to finish the upgrades by May 31.

“Checks on May 10 showed that the ‘damper’ on the APMS to control the smoke is still being upgraded.

“The nozzle at the APMS has been replaced, and the factory is in the midst of installing a water sprinkler to the system to reduce ‘fugitive dust’,” it said in a statement.

A damper is used for air pollution control, while fugitive dust is particulate matter resulting from commercial activities that are generated in the open air.

The DoE was responding to complaints by residents of a “burning smell”, which they claimed made them cough and suffer from sore throats. An estimated 5,000 people were said to be affected.

Today, the DoE said the factory was also asked to submit a report on the performance of its monitoring system to the department.

DoE said it had conducted checks at the premises on May 10 to ensure it carried out the improvements as ordered to it on March 16.

In March, the DoE had ordered the factory to use dry raw materials to avoid the release of thick white smoke, spray the road near the factory with a water sprinkler to reduce fugitive dust, upgrade the APMS and regularly maintain it.