Major League Baseball will review security procedures at ballparks in the wake of an attack on an umpire during a game Tuesday night between the Kansas City Royals and White Sox in Chicago.

Four men forced interruptions of the game at U.S. Cellular Field, formerly Comiskey Park, on Tuesday. The last man, Eric Dybas, 24, appeared to try to tackle umpire Laz Diaz, 40, before being apprehended. Dybas was charged with felony aggravated battery and misdemeanor criminal trespassing yesterday.

Police have not disclosed a motive for Dybas, who was scheduled to appear in court today, Cook County State's Attorney spokesman John Gorman said.

The attack comes seven months after Tom Gamboa, then the Royals' first-base coach, was beaten by a man and his son on the same field during a game between the same teams. This attack, on the Royals' first trip to Chicago since the Gamboa incident, occurred about 100 feet from where Gamboa was assaulted.

In the aftermath of Tuesday's incident, MLB dispatched its security chief, Kevin Hallinan, to Chicago to oversee security for last night's game. U.S. Cellular Field is scheduled to be the site of the All-Star Game in three months.

"Major League Baseball is extremely concerned with the lawless incidents that took place at U.S. Cellular Field [Tuesday] night," Commissioner Bud Selig said in a statement. "There is no place in baseball for such deplorable fan behavior and we urge that the guilty parties be prosecuted to the fullest extent of the law.

"Major League Baseball will re-examine the security efforts at all of our ballparks to prevent such incidents from occurring elsewhere."

The three men who jumped onto the field before Diaz was attacked were Jeffrey Adams, 25; Albert Skutnik, 25; and Tom Skutnik, 20, all of Chicago. They were charged with misdemeanor trespassing. Diaz, before charges against Dybas were announced, said he intended to press charges against his attacker.

"If I didn't that would be sending a bad message," he said. "These guys think that there isn't any price to pay, that they have to just spend time in the ballpark's detention area for a while. I want them to know that they will have to face jail time."

Diaz was attacked as he watched a routine fly ball being caught for the third out of the eighth inning. Dybas ran toward Diaz and grabbed his leg, which prompted Royals players to run to help Diaz from their first-base dugout. White Sox players and pitchers followed from the bullpen.

Diaz stands 5 feet 10 and weighs 210 pounds. He lifts weights every morning and said he received training in hand-to-hand combat when he was a Marine.

"I'm still a Marine," Diaz said. "Once a Marine, always a Marine."

Before Tuesday night's game, Diaz told Royals players not to worry about safety for Gamboa, who is now the team's bullpen coach and still has slight hearing loss from the attack. "I told them that anything happens," Diaz said, "and I have Gamby's back."

The typical umpiring rotation means that Diaz was behind home plate for last night's game and he wasn't at all worried about taking the field.

"I'll have on chest protector, shin guards, my cup and my mask," Diaz quipped. "I'll be covered head to toe."

But Diaz was concerned about the safety of his fellow umpires. He feared that his peers could be caught by surprise, just as he was, as they are paying attention to the game.

"I woke up this morning thinking that the guy who attacked me could have had a knife."

This is also not the first time Diaz has been assaulted during a game. Years ago, when he was umpiring a Little League game, Diaz ejected a 13-year-old boy for throwing his bat in anger. The boy's angry father stormed Diaz and "sucker-punched" him.

"I grabbed him and let's just say I hurt him more than he hurt me," Diaz said.

The White Sox had increased security for Tuesday night's game and beefed it up again for last night's game. Scott Reifert, the White Sox' director of public relations, noted that all four fans who hopped onto the field were apprehended quickly.

"Our security guys are off-duty Chicago policemen and there's nobody better trained to protect us than them," Reifert said. "We did everything in our power from a security standpoint to monitor the field. Ultimately it's the responsibility of the people in the seats to monitor how they act."

Reifert said that the White Sox have considered putting up barriers or placing seats farther from the field, but fans requested that they be "as close to the action as possible," Reifert said.

"Look at how close fans are at NBA games. They don't have this problem. At least 99 percent of the time, people behave well . . . but then you get four morons."

Security personnel at U.S. Cellular Field remove Eric Dybas who ran on field and grabbed umpire Laz Diaz during White Sox' game with Royals.GM Ken Williams, left, and Scott Reifert, White Sox' director of public relations, discuss incident.