Chandigarh, April 30 : Eleven people, including three children, were killed and four critically ill after inhaling a poisonous gas in a thickly populated Giaspura locality with several industrial and residential buildings in Punjab's Ludhiana on Sunday, officials said. Most of the victims were daily-wage migrants. The source of the gas leakage and its type are yet to be ascertained, said Deputy Commissioner Surabhi Malik. "Eleven people died and several complained of breathing problems following a leak of a gas, probably from manholes. The NDRF is on the spot and the entire area has been evacuated," she told the media. "They are collecting samples from manholes to know the type of gas and its origin. It is quite likely that some chemical reacted with methane in manholes. If it is unscientifically dumped by a factory owner, action will be initiated," she said. The National Disaster Response Force (NDRF) personnel have reached the spot and the entire area has been sealed and locals have been asked to move to safer places. Official sources said the condition of four people, who complained of breathing problems, is critical. They have been admitted to nearby hospitals. Shambhu Narayan said his 40-year-old nephew Kabilash Kumar, his wife Barsha Devi along with their three children -- Kalpana, Abhay Narayan, and Aryan -- died in the incident. Another local resident Ram Murat said his relative Saurav Goyal and his wife Triti Goyal, brother Gaurav Goyal along with his mother and eight-month-old boy fainted. The child is out of danger, while the couple and the mother have died. Gaurav's condition is critical. Expressing grief over the incident, Chief Minister Bhagwant Mann in a tweet said that the incident was very sad, and added that, "Police, government and NDRF teams are present at the spot. All possible help is being provided". The incident caused panic among the locals, some of whom even left their homes to save lives. AAP MP from Ludhiana, Sanjeev Arora, said most of the victims belonged to poor families. He has assured to provide treatment free of cost to the injured people at the Dayanand Medical College and Hospital (DMCH). He said he has also spoken to the DMCH Principal and made all arrangements in emergency if anyone is required to be shifted. /IANS