A plane believed to be carrying Missouri Gov. Mel Carnahan crashed in rain and fog on Monday night and the Democratic state party chairman said that the governor was ``missing.''

The governor and two other people were believed to have been on board the small, private plane that crashed 30 miles southwest of St. Louis late on Monday. It went down not long after takeoff.

Carnahan, 66, who has been governor of Missouri for eight years, was running for the Senate, locked in a neck-and-neck race with incumbent Republican Sen. John Ashcroft.

Carnahan had been in St. Louis for a fund raiser and was scheduled to attend a similar event at New Madrid, Missouri, in the evening before returning to Jefferson City, the state capital.

Ray Temple, the Democratic state chairman, said the governor was ``missing'' but declined to say that he had been killed.

CNN identified the other two people on board the plane as Carnahan's son and a longtime aide.

The sheriff's office in Jefferson County, where the crash occurred, said witnesses reported hearing a plane go into a dive and seeing a fireball.

The crash occurred as officials of both parties were gathering in St. Louis, site of the third presidential debate between Vice President Al Gore and Texas Gov. George Bush, which Carnahan was scheduled to attend Tuesday evening.

An aircraft believed to be Carnahan's crashed in rain and fog Monday night, and the Democratic state party chairman told reporters the plane had been "missing."  CNN reported the aircraft had been missing for more than three hours.

Jerry Nachtigal, the governor's spokesman in Jefferson City, the state capital, refused to comment on televised reports that Carnahan was on the plane.

"A plane has crashed in Jefferson County, and that's all we know," Nachtigal said.

The Missouri State Highway Patrol said a plane crashed about 25 miles south of St. Louis in a hilly, wooded area. The patrol said the debris from the crash was scattered, making identification of the plane difficult.

Ray Temple, the Democratic state chairman, said the governor was "missing" but declined to say that he had been killed.

The FAA reportedly confirmed that the plane was owned by Carnahan's law firm.

Carnahan, 66, is a licensed pilot, but is not rated to fly a twin-engine plane.

Carnahan and his son were both pilots but only the son was rated for instrument flying — which would have been necessary Monday evening — and he usually piloted the plane on campaign trips, aides said.

Tom Hunter, who lives near the crash site, told St. Louis television station KMOV he had heard the plane flying overhead.

"I thought, 'What a crazy person in this kind of weather.' Next thing, sounded like it was in a very steep dive, the engine was just screaming." He said he heard a loud explosion and the sky turned red. "That was it. It was total silence. I told my wife to call 911."

President Clinton called to express condolences to Carnahan's wife, Jean, from Egypt, where he was meeting with Mideast leaders. The couple has four children.

"He's (Clinton) known him (Carnahan) for a long time. They've worked together on a lot of issues," Clinton spokesman Jake Siewert said.

The crash was an eerie replay of an accident two decades ago in which Democratic congressman Jerry Litton was killed along with his family in a plane crash in the northwest part of the state on the evening he won the Missouri's Democratic gubernatorial nomination.

There was talk of postponing the third presidential debate between Vice President Al Gore and Texas Gov. George W. Bush in St. Louis on Tuesday night. But Carnahan's wife, Jean, insisted it go on. She said her husband would have wanted it that way.

In a statement, Bush praised Carnahan as ``a thoughtful, distinguished man who was dedicated to quality education and excellence in public service.'' Gore, who wore a black ribbon on his lapel, said he was ``deeply saddened'' and hailed Carnahan's work on education and other issues.

The Cessna 335 took off from an airport in Cahokia, Ill., across the Mississippi River from St. Louis, for a 145-mile flight to New Madrid, where the governor was to attend a Monday night rally.

Visibility at the time was three-fourths of a mile to two miles. The plane - registered to a law firm where Roger Carnahan was a partner - crashed 25 miles south of St. Louis in hilly, wooded country.

Sifford had paged the state Democratic Party director and told him the plane had encountered lightning and would return to St. Louis or Jefferson City, state Sen. Jerry Howard said.

Tom Hunter, who lives near the crash site, said he heard the plane flying overhead and thought it sounded like it was in a steep dive.

``I thought, `What a crazy person in this kind of weather,''' Hunter told St. Louis TV station KMOV. He said he heard an explosion and the sky turned red. ``That was it,'' he said. ``It was total silence. I told my wife to call 911.''

FAA spokesman Roland Herwig said there were no previous accidents, incidents or service difficulty reports on the 1980 Cessna.

Roger Carnahan received his pilot's license in 1988 and was authorized to fly aircraft both by sight and using only instruments. ``He was as close as it comes to the top when it comes to training,'' Cory said.

President Clinton called Carnahan's wife to express condolences while he was at the Mideast summit in Egypt.

``He's known him for a long time. They've worked together on a lot of issues,'' Clinton spokesman Jake Siewert said.

Lt. Gov. Roger Wilson will serve out the remainder of Carnahan's term, until Jan. 8.

The campaign, one of the key races in the Democrats' effort to retake control of the Senate, had been a dead heat for months. The most recent poll, taken for the St. Louis Post-Dispatch last month, gave Ashcroft 45 percent and Carnahan 43 percent, within the 4-point margin of error.

Carnahan's name will stay on the Nov. 7 ballot because the deadline to change it has passed. If Carnahan receives the most votes, Wilson, a Democrat, can appoint a replacement to serve until the next general election, in November 2002.

Carnahan, the son of a seven-term congressman, won his first public election at 26 as a municipal judge in his hometown of Rolla. He was elected to the Missouri House two years later and served two terms.

He served as state treasurer, and was elected lieutenant governor in 1988. Four years later, he won the governor's office in a landslide and was re-elected in 1996. He was barred by state law from seeking a third consecutive term.

The last governor to die in office was Florida's Lawton Chiles in 1998. The 68-year-old collapsed while exercising in the governor's mansion gymnasium. South Dakota Gov. George Mickelson died in 1993 when his state airplane slammed into a silo in Iowa.