Major League Baseball and the Houston Astros are investigating new allegations that the Texas team illegally used electronic equipment to steal opponents' pitching signs during their championship season two years ago, the Astros said Tuesday.

Four people associated with the Astros during the 2017 season said the team used a camera in the outfield to steal the signs that catchers flash to pitchers during home games, the subscription sports site The Athletic reported. That was the year the Astros won their only World Series title.

The Athletic quoted Mike Fiers, a pitcher who threw a no-hitter for the Astros in 2015, and three other unidentified people affiliated with the Astros as saying that during the 2017 season, players and other employees would monitor opposing catchers' signals using a camera in center field of the team's stadium, Minute Maid Park.

When they decided they had decoded the signals, Astros personnel would signal what pitch was coming to the batter — banging loudly on a trash can if it was a breaking ball or an off-speed pitch, according to The Athletic.

In a statement Tuesday, the Astros confirmed that the team and MLB had opened an investigation based on the report. The team said it would have no further comment.

MLB said in a separate statement on Wednesday that "numerous clubs expressed general concerns that other clubs were stealing their signs" during the 2017 season. In response, it said, it issued new procedures for the 2019 season "to provide comfort to clubs that other clubs were not using video during the game to decode and steal signs."

"After we review this new information, we will determine any necessary next steps," MLB said.

Stealing signs not only isn't illegal in baseball; it's a long and storied tradition. Sign-stealing isn't even mentioned in the official rules of the game.

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What's different with the Astros is the detailed description of the alleged use of electronic equipment, which is widely seen as cheating.

When the Boston Red Sox were accused of having sent electronic communications from their video replay room to an athletic trainer in the dugout in 2017, MLB Commissioner Rob Manfred made it clear that the sport's wider regulations "prohibit the use of electronic equipment" to steal signs or send information that could give a team an advantage.

The Astros are among the more polarizing teams in the major leagues.

Last month, the team fired Brandon Taubman as assistant general manager after he directed inappropriate comments at three female reporters in the team's locker room during the American League playoffs.

It's also not the first time that the Astros have been accused of using a camera to steal signs.

Last year, the Cleveland Indians warned the Boston Red Sox, the Astros' next opponent, that Indians security personnel had caught a man claiming to represent the Astros taking pictures of the Indians' dugout with a cellphone during the American League playoffs.

MLB said at the time that a "thorough investigation" had cleared the Astros and that the Astros employee was "monitoring the field to ensure that the opposing club was not violating any rules," not stealing signs.

In a thread posted Tuesday on Twitter, Carson Smith, a pitcher for the Boston Red Sox, added a new allegation. He said the Astros installed monitors in both teams' bullpens — but that while security guards and scorekeepers were constantly watching the monitor in the Astros' bullpen, the monitor in the opponents' bullpen didn't work.

It was also sketchy when the security guards/Crawford box scorekeepers kept constantly checking on our bullpen and looking up at the tv that coincidentally wasn’t working for us that series. — Carson Smith (@Carson_Smith39) November 12, 2019

Putting in cameras that both teams don’t have access to, to gain a competitive advantage.. you be the judge. — Carson Smith (@Carson_Smith39) November 12, 2019

"Astros went to extreme measures, undoubtedly still do, and it's paid off for them," Smith tweeted.

Aaron Judge, star outfielder for the New York Yankees, took a sarcastic angle:

Carlos Beltrán, a member of the 2017 Astros who was recently named as the new manager of the New York Mets, acknowledged Tuesday that the Astros did steal signs — but only the legal way, he said.

"I'm not aware of that camera," Beltrán told the New York Post by text message. "We were studying the opposite team every day."

"The game of baseball for years, guys have given location and if the catchers get lazy and the pitcher doesn't cover the signs from second base, of course players are going to take advantage," the Post quoted Beltrán as saying. "I don't call that cheating. I call that using small details to take advantage."

For his part, Fiers wasn't offered a new contract by the Astros after the 2017 season — he joined the Detroit Tigers in 2018 and pitched last season with the Oakland Athletics. The Athletic reported that he acknowledged having a "strained relationship" with the Astros because he told his new teams what the Astros were doing.

"I just want the game to be cleaned up a little bit because there are guys who are losing their jobs because they're going in there not knowing," Fiers told the website, adding: "We had a lot of young guys with Detroit trying to make a name and establish themselves. I wanted to help them out and say, 'Hey, this stuff really does go on. Just be prepared.'"