HARRISBURG — Fire officials had to close down a tractor pull at the Pennsylvania Farm Show complex after carbon monoxide sickened more than two dozen people.

The Patriot-News of Harrisburg reported the Mid-Atlantic Antique Tractor Super Pull was shut down Saturday after firefighters responding to a report of a sick man recorded carbon monoxide levels four times the permissible level.

Harrisburg Bureau of Fire Battalion Chief Michael Horst said the antique tractors burning modern fuel produced dangerously high levels of carbon monoxide. He said carbon monoxide sensors carried by firefighters went off as soon as they walked in the building.

The Patriot-News report said at least 25 people were sickened by the gas.

The state Agriculture Department is investigating.