Major League Baseball yesterday launched an investigation into a brawl between Texas Rangers players and Oakland Athletics fans Monday night in Oakland, Calif., which left a female fan with a bloodied and broken nose and resulted in the arrest early yesterday of Rangers relief pitcher Frank Francisco.

Francisco, a 25-year-old rookie, was charged with aggravated battery, a felony, for throwing a plastic chair into the stands near the Rangers' bullpen and striking two fans, including the unidentified woman. He was released two hours later on $15,000 bail, according to an Oakland Police spokesman, and is scheduled to appear this afternoon in Alameda County Superior Court.

Sandy Alderson, MLB's executive vice president of baseball operations, and security director Kevin Hallinan were on their way to Oakland's Network Associates Coliseum yesterday, and the A's added 10 security staff members to the visitors' bullpen and dugout areas for last night's game between the teams, along with several additional Oakland police officers.

The incident was the latest in a growing list of confrontations between players and fans in baseball. Last season at the Coliseum, an A's fan was arrested for throwing a cell phone that struck Rangers outfielder Carl Everett on the back of the head. In 2002, Kansas City Royals first base coach Tom Gamboa was attacked by a Chicago White Sox fan and his son, who ran onto the field during a game at Comiskey Park.

And in 2000, 19 Los Angeles Dodgers players and coaches were disciplined -- with penalties ranging from an eight-game suspension to various fines -- and three Chicago Cubs fans arrested following a brawl between Dodgers personnel and fans at Chicago's Wrigley Field.

"There is no excuse whatsoever for any attack of our fans by any of our players under any circumstances," Commissioner Bud Selig said in a statement.

The incident occurred as the Rangers batted in the top of the ninth inning Monday night, after a game-tying homer by Rangers second baseman Alfonso Soriano. As Rangers third baseman Hank Blalock batted, Rangers relievers suddenly charged into the stands near their bullpen -- which is located along the stands down the right field foul line -- as the Rangers' dugout also emptied and play was stopped.

Francisco, who had already pitched and was out of the game at the time, picked up a plastic chair used by a ballboy and threw it into the stands, striking a man in the head then deflecting and hitting the woman in the face. Several other Rangers players were also involved in the melee.

The woman, who was shown on television broadcasts of the game with a bloodied face, was taken to a nearby hospital and treated for cuts and a broken nose. Police identified her only as the wife of one of the fans believed to be heckling the players.

The A's and Rangers are locked in a tense playoff race in the American League West; Oakland eventually won, 7-6, in 10 innings Monday night. Last night, Texas won, 12-9, to cut the A's lead to five games, with Anaheim two games back.

After the game, Rangers Manager Buck Showalter accused fans of going "over the line." The Fort Worth Star-Telegram quoted an unnamed source as saying a fan used a racial slur directed at Francisco.

However, A's officials said the fans were guilty of nothing more than normal ballpark heckling.

"Based on the info we've got, at no time did any of our fans in the seating area engage in any improper action that would have warranted ejection from the stadium," A's spokesman Jim Young said yesterday. "The incident escalated when the players approached to confront the hecklers. And from what we know the heckling did not cross the line of what would be appropriate at a ballpark."

Rangers owner Tom Hicks issued a statement yesterday apologizing for the actions of his players, saying: "Their behavior, especially the injury to a fan, was unacceptable. Even in a difficult or abusive environment, players should never be provoked into such actions."

The Associated Press contributed to this report.

Rangers reliever Frank Francisco hurled a chair at fans during Monday's game in Oakland, Calif.An unidentified woman is treated after being hit by a chair thrown by the Rangers' Frank Francisco.