Muscat, Aug 4 - Four people were killed, including two children, when a four-wheel drive vehicle and a trailer collided in the Al Zamaim area of Al Wusta Governorate on Friday night, official sources have said. The children are aged three and 10 years, said a police official from Zamaim. Two persons were seriously injured in the incident, a Royal Oman Police (ROP) official said on Saturday. Investigations are under way. According to experts, factors that cause accidents on these long stretch of roads are poor visibility due to sandstorms, fatigue, speeding, reckless driving and non-compliance with traffic laws. Sixty-one per cent of accidents in the Sultanate occurred at night in June 2018.