In the 4pm incident, the victims, aged between 28 and 49, were carrying out maintenance work at the 5m-high tank.
The Selangor Fire and Rescue Department has withheld their identities for the time being, reported Bernama.
The blaze at the tank was put out within an hour after 30 firemen and five engines from the Batu Arang, Rawang and Selayang stations were deployed to the scene.
Selangor Fire and Rescue Department assistant director (operations) Mohd Sani Harul said the department, with the cooperation of the factory’s management, had deployed seven oil tankers to pump out the excess diesel from the tank.
Sani said the seven oil tankers would take turns making about three to four trips respectively to empty the tank.
“Once the diesel has been pumped out, our team would be able to search for the victims, believed to have fallen into the tank when the explosion took place,” the New Straits Times quoted Sani as saying.
He said a witness had seen the three victims conducting maintenance work at the tank just before it exploded.
Several family members were also seen waiting in front of the factory’s main gate.
One of the victims brother said he had waited outside the factory’s compound since 4pm yesterday.
“I called my brother several times but all my calls went unanswered. I am worried about him, I do not know what happened to him,” NST reported him as saying.
Meanwhile, the factory, Lafarge Malaysia Bhd, in a statement said the families of the victims had been informed and it was keeping them updated on the progress and providing the necessary support.
“Our prayers and thoughts are with them in their hour of need,” it said.