The St Louis Cardinals are under investigation by the FBI for hacking into the player database of fellow Major League baseball team, the Houston Astros.

It is thought to be the first known instance of a sports team hacking another.

The incident is being described as an "illegal breach of the Houston Astros' baseball operations database".

The New York Times reports that internal discussions about trades, proprietary statistics and scouting reports were all compromised. 

Major League Baseball says it "has been aware of and has fully cooperated with the federal investigation into the illegal breach of the Astros' baseball operations database,"

Tracing the technological breach led the FBI to a home that "some Cardinals officials lived in," the New York Times reported.

The breach is believed by law enforcement to be a vengeful plot against Houston Astros general manager Jeff Luhnow, who previously worked in scouting and player development for the Cardinals.

He had been a successful - but polarising - executive with the Cardinals until 2011, before being hired to take over as Astros manager.

And while considered unconventional, his approach helped restock the Houston minor-league system.

Luhnow is one the more statistics driven coaches in a game obsessed by numbers and is known as one of the more innovative thinkers in the sport.

While at the Cardinals, he was credited with drafting several players who have since become key parts of the team..

The Cardinals, the second most successful team in history after the New York Yankees, currently have the best record in baseball and sit top of the National League Central Division.

"The St. Louis Cardinals are aware of the investigation into the security breach of the Houston Astros’ database,” they said in a statement. “The team has fully cooperated with the investigation and will continue to do so. Given that this is an ongoing federal investigation, it is not appropriate for us to comment further.”