Taipei, April 3 : Flags will be flown at half mast across Taiwan for three days from Saturday to mourn the 50 victims of a fatal train derailment in Hualien county a day earlier. On Friday morning, the Taiwan Railways Administration (TRA) No. 408 Taroko train en route from Shulin, New Taipei, to Taitung, suddenly derailed as it entered the Daqingshui tunnel, The TRA said the derailment involved a maintenance truck which slid from a slope near a construction site above the rail track. The from of the eight-carriage train with 492 passengers and four crew members hit the vehicle shortly before entering a tunnel, dpa news agency quoted officials as saying. Prosecutors in Hualien were seeking an arrest warrant for a construction site manager believed to have failed to engage the vehicle's brake properly, state-run Central News Agency reported on Saturday. The manager was released by a court on Saturday on bail of 500,000 Taiwanese dollars ($17,516) and is not allowed to leave the country. Prosecutors said they would protest and seek an arrest warrant again. The Taiwan government revised the death toll, bringing it down from 51 to 50 due to a counting error. The TRA on Saturday named 44 of the victims, which included children and a 27-year-old French man, as authorities sought to identify the other bodies. Official statistics released on Saturday suggest that at least 178 people were injured in the accident. Forty of the injured would have to remain in hospital, including four patients in intensive care. Deputy Minister of Transportation and Communications Wang Kwo-tsai told a news conference on Saturday that the lack of a safety fence around the construction site, as required by the contract, was a huge management mistake. The TRA said that the accident is the worst train accident in the past seven decades in Taiwan. The Taiwan Railway Union urged the TRA to review its corporate culture, adding that, in recent years, the Administration had faced manpower shortage, a factor leading to insufficient control over the quality of contract companies. The TRA on Saturday said it would review its ticket policy as 120 passengers had standing tickets when the derailment occurred on the first day of a four-day break for Taiwan's annual tomb-sweeping tradition, which sees many Taiwanese people return home to pay tribute to their ancestors and clean up family tombs. The operator on Saturday began to remove damaged carriages stuck in the tunnel. President Tsai ing-wen visited injured people and victims' families in Hualien. Tsai also expressed appreciation for the international community's offer of condolences to families affected by the crash. /IANS