Officials across the state of Maine are investigating a series of bomb threats at Walmart stores Saturday night.Several Walmart stores were evacuated in York and Cumberland counties.Biddeford police confirmed that the Biddeford Walmart was evacuated just after 7:30 p.m. Saturday after an over-the-phone bomb threat was made. Investigators have since cleared the scene and the store has reopened.In Scarborough, police said they received a generic voice-automated threat to the Walmart located at 500 Gallery Blvd. at 7:49 p.m. The store was evacuated and police remained there until it was deemed safe to allow customers and employees back in. At this time, they have no further information. Scarborough police are encouraging anyone with information to contact the department at 207-883-6361.A similar threat to a Walmart in Windham came into Cumberland County dispatch Saturday evening. The store was evacuated for approximately two hours. Police cleared the scene by 10:09 p.m. Police in Windham are still investigating. They are not sure if the incident is related to the others, but plan to coordinate their investigation with other departments.In Somerset County, officials reported Walmart stores in Palmyra and and Houlton received automated threats.The caller's voice is described as male, and possibly generated through a computer.Other affected locations include stores in Somerset, Knox, Cumberland and York counties.Our sister station WMTW has learned that Walmart stores in Auburn, Augusta, Bangor, and Brewer were not affected.