TAIPEI - Grieving relatives of those who died in Taiwan's worst rail disaster in decades held prayers at the crash site on Saturday as salvage crews worked to remove the tangled mass of wrecked carriages.

Officials said Friday's devastating collision, which killed at least 51 people and injured nearly 190, was caused when a parked railway maintenance vehicle slipped down an embankment and onto the tracks.

A train packed with as many as 500 people at the start of a long holiday weekend then hit the truck just as it entered a narrow tunnel near the eastern coastal city of Hualien.

The truck driver -- who railway officials said may have failed to secure the parking brake properly -- has been released on bail after being interrogated by prosecutors and is barred from leaving Taiwan pending further investigation.

Around one hundred relatives held an emotional Taoist prayer ceremony near the crash site on Saturday afternoon, shaded under a canopy of black umbrellas.

Many wept openly as they surveyed the scene, some holding makeshift shrines inscribed with the names of those who died.

Some called out the names of their loved ones as other family members held them tight.

Rescuers described an appalling scene as they rushed into the tunnel and found the front of the train pulverised into a twisted mesh of metal.

"Car number eight had the most serious injuries and number of deaths," rescue worker Chang Zi-chen told reporters on Saturday, referring to the most forward passenger car.

"Basically more than half of the carriage was split open and bodies were all piled up together."

Specialist teams spent hours extracting victims and survivors on Friday.

On Saturday, focus shifted to removing carriages now blocking one half of the sole train line down Taiwan's remote and mountainous eastern coastline.

Two giant cranes were being used to move the carriages and rescuers said further bodies might still be found inside the most damaged cars inside the tunnel.

'REALLY DEVASTATING'

The Interior Ministry ordered all flags to be lowered to half-mast for three days while President Tsai Ing-wen visited the wounded in Hualien's hospitals.

"Government agencies are making an all-out effort in the hope of minimizing the impact of the disaster so the deceased can rest in peace and the injured can recover soon," she told reporters.

Friday's crash took place at the start of the Tomb Sweeping Festival, a four-day public holiday when many Taiwanese return to villages to tidy the graves of their ancestors.

A French and two American nationals were among the foreigners killed, authorities said. The youngest victim was 4-years-old.

Survivors gave terrifying testimony of their ordeal inside the train after the crash.

Many of those on board were standing in the aisles because the route was so busy with those leaving the capital Taipei and heading to their home villages.

"I saw bodies and body parts all over the place, it's really devastating," a man surnamed Lo told the Apple Daily newspaper.

"Humans are fragile and their lives are gone all of a sudden."

Investigators are focusing on how the maintenance truck could have slipped onto the tracks.

The driver was part of a team that conducts regular landslide checks on the mountainous route.

Officials said he may have failed to properly engage the parking brake.

Apple Daily reported that prosecutors had also raided the offices of the company contracted to do the trackside maintenance work.

TOURIST DRAW

Taiwan's eastern railway line is a popular tourist draw down its less populated eastern coastline.

With the help of multiple tunnels and bridges, it winds its way through towering mountains and dramatic gorges before entering the picturesque Huadong Valley.

Friday's crash took place near two of the most famous landmarks on the eastern shoreline -- the Tarako Gorge and dramatic Qingshui Cliffs.

A world-class bullet train system also serves the heavily populated western side of the island.

Friday's crash looks set to be one of Taiwan's worst railway accidents on record.

The last major train derailment in Taiwan was in 2018 and left 18 people dead on the same eastern line.

That crash was the island's worst since 1991, when 30 passengers were killed.

Other major crashes that killed dozens have taken place in 1981, 1978 and 1961.

Taiwan's most deadly rail disaster on record was in 1948 when a train caught fire and 64 people perished.