The big cat was found inside the plant's engine department Thursday morning.
The plant premises were sealed off, and police and forest officials launched a search operation.
A police official told ANI that workers arriving for the morning shift were asked to wait outside.
Finally, the morning shift at the plant -- staffed by some 2.000 workers -- was cancelled.
Then, so was the afternoon shift.
A police offical told PTI that a forest department team was called in to find the animal.
The team came armed with nets and tranquiliser guns -- but have not been able to find the animal.
The Times of India reported that the leopard-rescue operation was expected to continue till nighttime.
"It is a very tricky situation. There are thousands of machineries installed on 2 meter-high elevated platforms. I don't think it is possible to rescue the leopard. The leopard generally hides itself during the day. It is expected to come out at night," TOI reported a wildlife inspector carrying out the rescue operation as saying.
TOI reported Vinod Kumar, conservator of forests, Gurgaon circle, as saying "We hope that the leopard is rescued at the earliest. However, it is a little difficult task as the area is very big. At night, the leopard generally comes out. We might need to put live bait traps in the evening/night. As there are cameras on all exits, we should be able to track its exit."