Multiple people are feared dead in Australia after their bus crashed Sunday as they returned from a wedding in a wine region in the east of the country. The bus rolled over at a roundabout near the New South Wales town of Greta in the Hunter region, also referred to as the Hunter Valley, about two and a half hours northwest of Sydney. Authorities said initial reports suggest at least 10 people were killed and 25 hospitalized, with some flown to Sydney for medical care. The bus driver, 58, was arrested, according to police. He was not injured in the incident, police said. The bus had been carrying people returning from celebrations when it crashed, NSW state Premier Chris Minns said. Minns called the crash a "profoundly tragic event," adding that residents of the region "will be shocked and saddened." The crash occurred around 23:30 local time. Emergency reports came in just before midnight, with police dispatching multiple helicopters, firefighting units and ambulances to the scene. NSW Police Acting Assistant Commissioner Tracy Chapman said the guests were travelling to Singleton "presumably for their accommodation". She said it was too early to comment on the circumstances of the crash, but police had "sufficient information" to bring charges against the driver. Chapman did not specify what those charges were, but said the crash site is being treated as a crime scene. "He's under arrest. He's been the driver of a motor vehicle collision where there have been fatal injuries and there will be charges pending," she added. Chapman also said there had been heavy fog in the area around the time of the crash. The number of fatalities could increase, with 25 passengers taken to hospital -- two of them airlifted from the crash, Ms Chapman said. She added that the bus is still on its side and people could be trapped underneath, and a crane will be brought to the scene "at some stage" to lift the bus. Police are still trying to identify all the people on the bus but "as far as we're aware there are no children involved," Chapman said. As of Monday morning, the bus was still on its side; police said the bodies of those killed had not yet been removed, and it was possible more people could be discovered under the bus. Australian Prime Minister Anthony Albanese expressed his condolences following the "horrific" crash. "All Australians waking up to tragic news from the Hunter send our deepest sympathies to the loved ones of those killed in this horrific bus tragedy," Albanese said on Twitter. "For a day of joy to end in such devastating loss is cruel indeed. Our thoughts are also with those who have been injured." In a statement Monday, the wedding venue said it was supporting guests who need their help, adding that it wished to protect their privacy. Hunter Valley is known for its vineyards and native bushland, making it a popular spot for tourists and group outings. A guest at the wedding said the day had been a "fairy tale" until news of the accident broke. "We all started panicking," he told 7 News. Police said they are still working to identify the crash victims and contact their next of kin. "Family and friends of a person who may have been on board the bus are urged to contact Cessnock Police Station," they said in a statement. — Agencies