The partner of the gunman behind the worst mass shooting in America's history, which claimed the lives of at least 50 people, has been identified as an Australian citizen.

Marilou Danley, 62, was spoken to by police in the early hours of Monday morning after her 'companion', Stephen Paddock, 64, opened fire on a music festival just off the Las Vegas strip.

Ms Danley, who shared a house in the city with the mass murderer, holds an Australian passport and is from the Philippines, The Australian reported.

Police say they do not believe at this time Ms Danley is involved in or connected to the shooting. Las Vegas Sheriff Joseph Lombardo confirmed they located her outside of the country.

They say she was not with Mr Paddock at the time he checked in and also believe Mr Paddock was 'utilising some of her identification.'

She lived on the Gold Coast in Queensland for more than a decade with her former husband, an Australian man, who has since passed away. She moved to the United States 20 years ago.

Ms Danley described herself on her Facebook page as a 'proud mom and grandma'. She worked at one of the casinos in the city.

'I would never have thought she would be tied up in anything like this,' a friend told the Courier Mail.

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Marilou Danley (pictured), who shared a house in the city with the mass murderer, holds an Australian passport and is believed to be of Indonesian heritage

Marilou Danley was detained by police in the early hours of Monday morning after her 'companion', Stephen Paddock opened fire on a music festival just off the Las Vegas strip

Mr Paddock's brother, Eric, told CBS Ms Danley was 'a nice lady' but said he wasn't aware if the two were married.

'I've met her three or four times, she's got a Facebook page, she sends cookies to my mum,' he said.

'We were worried he might have hurt her too.'

Police say Mr Paddock, described as a local man, opened fire on the Route 91 Harvest Festival in Las Vegas Village from a room across the street in the Mandalay Bay Hotel shortly after 10pm.

Officers confirmed Paddock was shot and killed after they breached a room in the hotel, where he had stashed an 'arsenal' of weapons used during the massacre.

Investigators are now raiding the Mesquite home he shared with Marilou Danley, described as his 'companion', who was detained for questioning in the early hours of Monday morning.

She and the shooter are said to be companions; their precise relationship has not been explained.

Sheriff Joseph Lombardo, of the Las Vegas Metropolitan Police Department, said investigations are still ongoing and police have not yet determined a motive.

She and the shooter are said to be roommates or companions; their precise relationship has not been explained

She and the shooter are said to be companions; their precise relationship has not been explained

Police say Mr Paddock, described as a local man, opened fire on the Route 91 Harvest Festival in Las Vegas Village from a room across the street in the Mandalay Bay Hotel shortly after 10pm

Revellers described hearing automatic rounds during the concert sparking mass panic and chaos.

Thousands fled as bursts of gunfire could be heard for more than five minutes, at least 50 were killed and 200 more injured.

A police handout said Ms Danley was being sought for questioning. The public were urged to call 911 if she was spotted.

Police were reported to be searching his house in the early hours of Monday morning, though have not given any indication of a motive.

Revellers described hearing automatic rounds during the concert sparking mass panic and chaos

Thousands fled as bursts of gunfire could be heard for more than five minutes, at least 50 were killed and 200 more injured

Kevin Comerford, Nicole Shipman (pictured top of left) and her daughter Maddy Aspinall (bottom of left), 14, from Grafton in NSW, were in Las Vegas for one night only after a dance academy tour in the US had finished

An Australian couple and their teenage daughter who were caught up in the crossfire said the experience was the 'scariest night of our life'.

Kevin Comerford, Nicole Shipman and her daughter Maddy Aspinall had been staying overnight in las Vegas attending a dance academy tour.

The family from Grafton in regional New South Wales were told to walk with their hands in the air across an empty casino following the shooting that claimed at least 50 lives.

'This was supposed to be a one night special stop because we'd never been to Las Vegas before ... we were planning to live it up for one night and we've had probably the scariest night of our life,' Mr Comerford told AAP.

They had been staying in a hotel roughly two blocks from where the shooting took place and said it took them an hour to get safely back to their room.

Mr Comerford said his partner's 14-year-old daughter was struggling with the situation.

'The police had us walk through the empty casino with our hands above our head and it became very, very real for her then,' he said.

'That's when she got very upset. She's been a brave girl.'

Revellers described hearing automatic rounds during the concert sparking mass panic and chaos

Thousands fled as bursts of gunfire could be heard for more than five minutes, at least 50 were killed and 200 more injured

A Perth woman told Fairfax she only checked out of the Mandalay the morning of the shooting and had been rushed out of another casino as the incident unfolded.

'We were over at New York New York having some drinks with friends from Perth and there were police and ambulance and fire brigade everywhere and bodies on the street,' she said.

'People were terrified running around... we got in the lift to come up to the room where I my friends were staying and people were screaming and terrified. I've never seen faces like theirs before.'

Australia's Consulate General in Los Angeles is currently speaking with police to determine if any Australians have been victims of the shooting.

'If you have any concerns for the welfare of family and friends in the Las Vegas area, you should attempt to contact them directly,' a Department of Foreign Affairs and Trade spokeswoman told AAP.

People unable to make contact with loved ones should phone the DFAT emergency hotline: 1300 555 135, or +61 2 6261 3305