Sydney - A man was arrested in Sydney on Thursday and a bomb disposal squad was examining his car after he drove it into an underground police station car park.Australian police said there was "nothing to indicate" a link to terrorism, but would not rule out the possibility.The man, aged in his 60s, parked his car in the driveway of the station in the western suburb of Merrylands about 19:00 (09:00 GMT), New South Wales state police said, adding that the inside of the vehicle burst into flames as an officer approached it."The man then drove that vehicle down the driveway and collided with the roller shutter door [of the car park] under the police station," Assistant Commissioner Denis Clifford told reporters outside the station."He has been treated by ambulance and conveyed to hospital in a serious condition with what I understand are very serious burns."Clifford said there was "nothing to indicate this is in anyway related to terrorism"."We'll keep an open mind, but we are not moving in that way at this stage," he said, adding that "we have nothing to indicate he is linked to anyone else".Mental health issues The man has a history of mental health issues, police told AFP earlier.No-one else was hurt in the incident, police added.The Australian government lifted its terror threat level to high in September 2014 and recently said nine terror events had been prevented since then.But several have taken place, including the terror-linked murder of a police employee in Sydney in October."Police are on high alert, and we've been that way for some time due to events here and overseas," Clifford said."It's a situation police are well aware of... it's just a miracle that no-one else was seriously injured."