A few words muttered by a semiconscious man, one of two persons seriously injured when a car crashed into a tour bus near the Washington Monument last night, led police to believe for several anxious minutes that the car might contain a bomb.

No explosives were found, but police blocked off 15th Street NW between Constitution and Independence avenues, disrupting late night tourist traffic at the monument while the bomb squad moved in to search the car after the 9 a.m. incident. The crash caused minor injuries to three children and three adults who were on the bus.

Police said the semiconscious man, Steven M. Nagy, 30, of Oakland, Calif., a passenger in the car, seemed to mumble something about a bomb while a U.S. Park Police rescue helicopter was flying him to the Washington Hospital Center where he later was listed in serious condition.

"We thought, with the recent rash of bombings on the East Coast and all, we should be extra cautious," said Park Police Sgt. Tom Bradley.

The driver of the car, James L. Makepeace, 23, of 5375 Duke St., Alexandria, was admitted in fair condition to George Washington University Hospital, with a hip fracture and possible head and abdomen injuries.

The bus had stopped at the 15th Street NW entrance to the Washington Monument grounds to pick up a school tour group from Middlebury, Conn., when the car driven southbound by Makepeace veered off 15th Street onto the grass and then back onto the street, striking the left rear of the bus. Three 12- to 13-year-old passengers on the bus were treated for minor injuries at Children's Hospital and released. Two adult chaperones and the bus driver were treated and released from Washington Hospital Center.