Indore: A child died and another was in a critical condition at Maharaja Yeshwantrao Hospital here after they were mistakenly given nitrous oxide, a widely used anaesthetic, to breathe in place of oxygen, a police officer said on Sunday. The incident on Sunday led to the arrest of a contractor who installed the gas pipes in the 'modular paediatric operation theatre' where the children were treated, said O.S. Bhadoria, chief of Sanyogitaganj police station here. The operation theatre has been sealed and a first information report (FIR) has been registered, he said. Ayush, 8, died on Friday after he was administered 'oxygen' through a mask; he died in the operation theatre. Rajveer, who is only 18 months old, is in serious condition after being administered 'oxygen' on Saturday in the same operation theatre. Sumit Shukla, a surgeon at the hospital, told reporters that there are two separate colour-coded pipes in the operation theatre, one for oxygen and the other for nitrous oxide which is widely used medically for its anaesthetic and analgesic effects. It seemed that the pipe meant to supply oxygen yielded the wrong gas, he said. Shukla said the hospital was conducting its own inquiry as to how the horrible mix-up took place. Some people, however, said the hospital has been guilty of gross medical negligence and is evading its responsibility in the matter. Local legislator and Congress leader Jitu Patwari said the culprits are among the administration and the hospital authorities and they are the ones who should face stern action. Contractor Rajendra Chadhary, who has been arrested, said he has been made a scapegoat. "My job was only to install the pipes. Using those pipes to supply gas was the job of the hospital," he said. Maharaja Yeshwantrao Hospital is the largest government hospital in Indore city.