Washington, Sep 14: A series of gas explosions damaged at least 23 buildings and residences, and injured many in several Massachusetts towns in the US, state authorities said on Thursday.The incident began about 5 p.m. when several explosions occurred in buildings in the towns of Lawrence, Andover and North Andover.The reason for the blasts, so far, is unknown, Efe reported.Massachusetts state police said at least 23 explosions and subsequent fires had occurred at a number of different addresses, although local media reported that more blasts had taken place in nearby areas.The fires were attributed to possible problems with the natural gas system and security forces urged local residents to leave their homes immediately if they smell gas or suspect that they could catch fire.Local media reported that local fire chief Michael Mansfield said that between 25 and 30 active fires were being battled in Andover and at least 18 more in Lawrence."There are multiple basement fires in Andover. It's some kind of gas issue," Andover Police Department spokesman Lt. Edward Guy said."We urge residents if they are smelling gas to get out of the house and contact 911. We will get units out there," he added.