An Indian court convicted 31 workers on Friday over an outburst of deadly violence at a car plant in 2012, including 13 for murder, during one of the country’s worst episodes of labor unrest.

The court cleared 117 accused who were also facing charges of murder, arson and rioting after hundreds of workers clashed with managers over wages and appointments at the Maruti Suzuki factory in Manesar.

The hearing in Gurgaon, on the outskirts of New Delhi, found 13 workers guilty of murdering Awanish Kumar Dev, whose charred body was found in the remains of a building following the riots in July 2012.

Dev, who was a human resources manager, died after he failed to escape a blaze which was started by workers who went on the rampage in Manesar, which is around two hours’ drive southwest of the capital.

The additional sessions court ruled that 18 others were guilty of rioting, arson and damaging property and will announce the sentences on March 17.

A lawyer for those found guilty on Friday immediately announced plans to appeal against the convictions.

“We will challenge the conviction in a higher court,” Monu Kuhar, part of the defense team, told AFP.

Hundreds of policemen in riot gear were deployed at the court and outside automakers’ offices over threats by workers to mobilize large-scale protests if their colleagues “did not get justice.”

On Thursday, thousands of workers staged a brief work stoppage at Maruti and other auto companies’ offices to express solidarity with the accused.

Prosecutors told the court that the attack was the result of a conspiracy by workers, who were at loggerheads with the management over wages and plans to set up a union at the workplace.

The plant, which manufactures nearly 700,000 cars annually, was shut for 60 days prior to the deadly violence.

Investigators said more than a thousand workers had charged at the administration block and attacked the officials with iron rods and car parts such as axles at the plant.

They beat up officers, including Dev, breaking his limbs, leaving him immobile and leaving him unable to flee the flames.

More than 100 other managers were injured in the day-long violence that shut the plant for over a month.

But union leaders claim it was triggered by an argument between a supervisor and a casual employee, who was abused over his caste.

Maruti Suzuki, a subsidiary of Japanese automobile major Suzuki, has a market share of 51 percent in India.

Workplace violence is not uncommon in India, where workers are often locked in conflict with the management over wages and hostile working conditions, but it is rare for major corporates to be targeted.

Labor unions frequently accuse management of hiring cheap labor through short-term contracts which makes it easier for firms to dismiss workers.

Last year a court in Tamil Nadu sentenced eight workers to life imprisonment over the lynching of a senior manager in violence sparked by the dismissal of 42 workers at an automobile spare parts factory.

In June 2014, around 200 workers bludgeoned to death the owner of a jute firm in West Bengal with iron rods and stones after the management of the loss-making company increased their working hours.