Two men were killed and two others seriously injured in an accident in New Madrid County, Mo., and a 20-year-old man was killed in a single-car accident on Boaz Road in Illinois.

Two men were also seriously injured when a tractor-trailer collided with two Missouri Highway Department vehicles in New Madrid County.

All of the accidents occurred Wednesday.

In the fatal New Madrid County accident, Monroe Lipsey, 61, and Michael Adams, 26, both of Inwood, N.Y., were pronounced dead at the scene when the car Lipsey was driving struck a pickup truck driven by Luther Keene on East Outer Road one mile north of Portageville.

Keene, 40, of Portageville was seriously injured and taken to Missouri Delta Hospital in Sikeston. Jessie Highsmith, 33, of Inwood, N.Y., a passenger in Lipsey's vehicle, was also listed in serious condition at Pemiscot County Hospital in Caruthersville.

Police said Lipsey's vehicle was traveling north in the southbound lane of East Outer Road when it struck Keene's vehicle head on. It is possible that Lipsey thought he was traveling on the interstate and mistook the two-lane road for the northbound lane of Interstate-55, police said.

No one in Lipsey's vehicle was wearing seat belts.

The 20-year-old man killed in Illinois was identified by Illinois State Police as Jason L. Vines, 20, of Karnack, Ill. Police said he failed to stop at the intersection of Boaz Road and Illinois Highway 169. The vehicle ran off the road and overturned in a creek.

In the other New Madrid County accident, Gerald Scherer, 53, of Portageville was flown to Southeast Missouri Hospital in Cape Girardeau after the highway department truck he was in was struck from behind by a tractor-trailer driven by Sam Parker, 42, of Johnsville, S.C. Parker was also listed in serious condition at Missouri Delta Hospital in Sikeston.

The patrol said Parker's truck was traveling north when it collided with the highway department truck as it was parked facing north in a northbound lane of Interstate-55 at about 1:15 p.m. The tractor-trailer continued forward and struck an unoccupied highway department oil mixer, also parked, which hit another oil mixer. Scherer's truck overturned into the median and one of the oil mixers was overturned into a ditch.

The incident is under investigation and no charges have been filed.