Bengaluru,  An explosion in a molten plastic paint machine near the underpass of the second terminal of the Kempegowda International Airport caused injury to six workers early Monday, the police said.

According to the airport police, two of the six workers, Ajay Kumar and Siraj are critical after suffering over 40 per cent burns.

The others were identified as Avinash, Goutam, Prashanth, Nagesh -- all have been admitted to Victoria Hospital.

The police said that the workers were using thermoplastic road marking machine to paint the zebra crossing and signages on the roads leading upto the airport terminal.

The exact cause of fire is still not known but prima facie investigations have revealed that a "substantial amount" of paint vapour and mist could have been released causing the accident.

"Perhaps storage of paint material, overspray could have drift into surrounding areas, mixing with the air and accumulating in enclosed or unventilated areas leading to a blast," the police explained.

The blaze spread to the underpass in no time.

"Security guards rushed to the spot after hearing the workers' cries and took them to hospital. Fire-fighters soon arrived at the scene but it wasn't before two hours that they doused the flames," the police said.

This is the first fire accident to have happened during the construction of the airport's second terminal, which has been going on for the past few years.

The police said that they have registered a complaint against the company under contract for negligence and failure to take precautions for the safety of workers.

The Kempegowda International Airport, the third-biggest airport in India, began constructing a garden terminal called T2 to accommodate the increasing passenger traffic in 2019 but due to prolonged lockdown and outbreak of pandemic in March 2020, the project is likely to be completed in 2022 second quarter instead of March this year.

The terminal will feature trees, small gardens and ponds with local species of plants. It is expected to serve approximately 25 million passengers a year.

The terminal's design is inspired from Bengaluru's ubiquitous tag as a 'Garden City'.

Passageways throughout the terminal will connect the passengers with nature. The ceiling at the entrance, check-in and security area will feature hanging bells.