Relatives of people who died in a bus crash mourn their loved ones at a memorial ritual in Taipei on Tuesday. At least 33 people were killed in the incident on Monday.Guo Jiquan / For China Daily

Investigators were looking into excessive speed as the possible cause of a bus crash in Taiwan that killed 33 people and injured several others in the island's worst road accident in more than three decades, an official said on Tuesday.

The tour bus crashed near Taipei on Monday night, with television footage showing the bus careening toward a road barrier before flipping on its side.

Of the 44 people on the bus, 30 were pronounced dead at the scene and three died in hospital, the fire department said, adding that 11 people were still being treated in hospitals around Taipei.

Families of the victims arrived at the site after the accident, chanting sutras and praying.

Many of the passengers were senior citizens, although the age range was from early 20s to late 60s, according to city authorities.

The trip had been arranged by the Tieh Lien Hua Travel Agency, according to Taiwan's tourism bureau.

An official with the agency said the tourists were "likely" all from Taiwan, but that it was still studying passenger information.

Highway police spokesman Ma Ling-wen said the speed limit on the ramp was 40 kilometers per hour, but it was not clear how fast the bus had been going. Ma said speed had not yet been ruled out as a cause of the crash.

Local television footage showed a video of the bus shot from behind flipping onto its side and skidding toward the hillside after it hit a road barrier when negotiating a highway interchange curve.

Ambulances and fire trucks were lined up along the bend of the road as rescue workers used a crane to lift the battered bus from its wheels, after all the passengers were pulled from the wreckage.

The crash is the latest accident involving a tour bus in Taiwan. Earlier this month, another tour bus carrying tourists from the Chinese mainland crashed into a bridge in southern Taiwan, injuring some passengers.