The leakage was noticed at around 8 am and it was plugged by 10.30 am, they said, adding, the operations of the plant, which was shut down temporarily, resumed by 11 am.
The guage of the tanker was found to have been damaged from where the gas leaked, the sources said.
Eight LPG tankers were parked near the plant when the leakage took place.
Joint efforts by Fire force, police and IOC officials helped plug the leak.