The case was registered at the Parwanoo police station under section 336 of the IPC (act of negligence endangering human life or personal safety of others) for the leakage on Saturday.
No one was, however, injured in the mishap, a police officer said.
Executive Engineer of the State Pollution Control Board Deepak Aggarwal said a major industrial disaster was averted due to moist weather conditions.
"The incident could have had serious impact on a large number of people, but the gas dissolved and diluted due to rains and moisture in atmosphere," he said.
The Board, however, would probe if norms and provisions were violated by the firm, he added.
With chemical manufacturing units mushrooming across Parwanoo, Baddi, Brotiwala and Nalagarh areas of Solan and Una industrial hubs; air, water and soil pollution have already reached saturation levels.