Major League Baseball's investigation into illegal sign stealing is expected to expand beyond the 2017 Houston Astros and look into whether other teams, including the 2019 Astros, used technology to aid hitters, sources familiar with the situation told ESPN.

The fallout from former Astros pitcher Mike Fiers telling The Athletic that the 2017 Astros used a center-field camera feed in a monitor near the dugout to steal and relay signs has rocked the sport and brought into question the methods used by people involved in at least the past three World Series, sources said.

The initial stages of the investigation already have begun, sources said, with league personnel contacting people from both the Astros and Boston Red Sox organizations Wednesday. The league is attempting to cull tangible evidence from the widespread paranoia of front offices and teams around the game about others cheating and has indicated it will consider levying long suspensions against interviewees who are found to have lied, according to sources.

While there is considerable crossover between the 2017 and 2019 Astros teams, multiple witnesses who were not with the 2017 team are expected to be interviewed, sources said.

Among those the league plans to interview in its investigation are Astros manager AJ Hinch, Red Sox manager Alex Cora and New York Mets manager Carlos Beltran, according to sources. The three were part of the 2017 Astros championship team -- Hinch the manager, Cora the bench coach and Beltran a player. Their involvement in the investigation was first reported by The Athletic.

MLB, sources told ESPN, spoke Wednesday with former Astros bullpen coach Craig Bjornson, who joined the Red Sox with Cora in 2018, the year they won a World Series. MLB also intends to interview former Astros assistant general manager Brandon Taubman, though he has retained a lawyer through whom he is communicating, according to sources.

As baseball's general managers meetings neared their Thursday conclusion in Scottsdale, Arizona, the league was grappling with the scope of the investigation and how wide-ranging it could become, sources said.

MLB's department of investigations has begun gathering a wide-ranging list of potential interviewees and is expected to talk with players as well as managers, coaches and other team personnel, sources said.

Any conversations with players would need approval from the Major League Baseball Players Association. When the league investigated the Red Sox in 2017 for the illegal use of an Apple Watch, the union participated in interviews with the players.

The penalties for illegal activity are determined by commissioner Rob Manfred, though if the league can prove wrongdoing, the severity could be unlike anything seen in the sport's recent history, sources said.

The heaviest penalty assessed to a team during Manfred's tenure was a $2 million fine and the forfeiture of two top draft picks by the St. Louis Cardinals in January 2017 for a scheme in which they stole scouting information from the Astros' computerized database. The Cardinals' scouting director, Chris Correa, was banned for life from the sport and went to prison. Former Atlanta Braves general manager John Coppolella was banned 10 months later for lying about the team's circumvention of international signing rules. The Red Sox in 2016 were barred from signing international players for a year after running afoul of the signing-bonus statutes.

Before the 2019 season, MLB instituted new rules to clamp down on illegal sign stealing. Unsanctioned cameras between the foul poles were outlawed, an eight-second delay on in-house camera feeds was mandated and an official sat in replay rooms off the dugout to monitor teams to try to prevent cheating.

The allegations against the Astros are the first to include on-the-record comments outlining a purported scheme. "That's not playing the game the right way," Fiers told The Athletic.

Fiers described a scenario in which the Astros received the feed near the dugout, decoded the sign flashed by the catcher and, if the sign was for an off-speed pitch, hit a trash can to signal to the hitter that it wasn't a fastball, according to Fiers.

Though the theft of signs is an avowed part of baseball, the game's unwritten rules long have limited it to players at second base picking the sign and signaling hitters through slight, prescribed movements. The use of technology is widely considered beyond the pale and has left the sport facing questions that, if evidence corroborates Fiers' accusations and exposes wrongdoing beyond that, could strike at the heart of the sport's integrity.

"I'm not aware of that camera," Beltran, who was hired by the Mets less than two weeks ago, told the New York Post in a text message Wednesday. "We were studying the opposite team every day."

During the 2019 American League Championship Series, after the New York Yankees called the league to report whistling from the Astros' dugout during Game 1, Hinch denied any wrongdoing.

When asked about the Astros on Wednesday, Dodgers president Andrew Friedman, whose team lost to Houston over seven games in the 2017 World Series and to Boston in five in 2018, declined to talk about specific allegations, fearing they would sound like "sour grapes."