CHEONAN -- Ahn Cheol-soo, presidential candidate of the minor opposition People's Party (PP), has paid his respects to two campaign workers who were found dead in a bus apparently from gas poisoning, according to party officials Wednesday.

The deceased workers, a local campaign chief and a bus driver, were found unconscious inside a campaign bus in Cheonan, about 90 kilometers south of Seoul, Tuesday evening. They were later pronounced dead at hospitals.

Party officials said they are believed to have died possibly due to poisoning from carbon monoxide produced from a generator used in operating a large LED screen installed on the exterior of the bus.

Ahn, who has suspended his campaign amid the incident, paid his respects to the late campaign chief at a funeral home set up at Dankuk University Hospital in Cheonan on Tuesday evening. He later offered condolences to the deceased bus driver at a separate funeral home at the nearby Soon Chun Hyang University Hospital in the city.

He declined to answer questions from reporters at the hospitals.

A similar incident involving an Ahn campaign bus was also reported in the eastern city of Wonju on Tuesday, reportedly leaving one person in a grave condition.

Police are looking into the exact cause of the deaths.

Authorities have moved the bus to a nearby police station and have examined the LED and other details of the bus Tuesday.

Officials reportedly plan to question employees at the LED screen company and how much they were aware of the danger of carbon monoxide poisoning.

The party said it has been operating 18 buses across the country. (Yonhap)