Islamabad : Three people were killed and 10 others injured when the dome of an under-construction mosque collapsed in Lahore, local media reported. About 25 labourers were working at the mosque when the dome collapsed on Thursday, Xinhua news agency.The injured people were shifted to a nearby hospital where two of them were in critical condition. Police has launched investigation into the incident. According to preliminary reports, substandard construction material was the reason of the collapse.