A suspected gas leak in the drug manufacturing plant of Dr Reddy's Laboratories in Bollaram on the outskirts of Hyderabad killed two workers early on Wednesday morning.
The workers, on night duty, apparently fell unconscious after inhaling nitrogen gas and died before other employees could notice, police said.
The deceased were identified as Sridhar Reddy, 30, a production chemist, and Deepak Jena, 32, a contract worker from Orissa.
The police said the "preliminary inquiry revealed that the duo died due to inhalation of nitrogen gas".
A case has been registered under Section 304 of IPC (causing death by negligence) and Section 22 of Dangerous Machines (Regulation) Act (Compensation to Operator in Case of Death or Injury) against the company management.
"We booked a case against the management and are awaiting post-mortem and other reports," SP Sundar Kumar Das said. No safety equipment or notices were found, he added.
Bala Kishore, the director of factories, said they were yet to conclude the investigation.
"At the time of the accident, the deceased were handling the process of micronisation of Omeprazole powder. Apart from these two persons, no others were affected. The incident happened in the "clean room" located in one of the production blocks," Dr Reddy's said in a statement.
"Manufacturing in the rest of the facility is continuing... Investigations by multiple authorities... are in progress and we will share full details once the investigations are concluded," it added.
The United States Food and Drug Administration-approved plant produces active pharmaceutical ingredients.
(With PTI inputs)