Police in Las Vegas have tracked down Marilou Danley, the woman they wanted to speak to in association with the deadliest mass shooting in US history.

Las Vegas police tweeted: "We have located the vehicles in question, and we are confident we have located the female person of interest."

But authorities later ruled her out of their investigations, "Marilou Danley is no longer being sought out as a person of interest. LVMPD detectives have made contact with her and do not believe she is involved with the shooting on the strip," local police said.

The announcement came when they also confirmed that the death toll was at least 50 with more than 200 injured in the late-night attack at a music festival along the Vegas Strip.

The Las Vegas shooter has been identified as 64-year-old Stephen Paddock, responsible for the deaths of at least 20 people and injuring hundreds more at the Route 91 Harvest country music festival.

Paddock is thought to have opened fire on a concert from the Mandalay Bay Hotel in Las Vegas before being killed by police who engaged the shooter and killed him on the 32nd floor of the Mandalay Bay Hotel and Casino across the street from the festival.

Marilou Danley Las Vegas suspect
Police in Las Vegas are looking for Marilou Danley who being sought for questioning re the investigation into the active shooter incident in Las Vegas Las Vegas Metropolitan Police Department

Police in Nevada revealed that the pair live together in a small retirement town northeast of Las Vegas, they have also had no prior involvements with the police.

No motive was provided about the attacker, but it is so far thought that he acted alone.

Videos and photographs from the scene show people running from the area as well as ducking to the sound of automatic gun fire. Roads are closed or blocked in a lockdown in parts of the strip.

Police have urged people to stay away from the area while the investigation continues.