FBI agents are struggling to pinpoint exactly who within the St. Louis Cardinals organization repeatedly hacked into the Houston Astros' closely guarded baseball intelligence network.

The investigation is focused on a group of Cardinals employees who specialize in statistical analysis and computer programming and had access to a computer in a residence near the team's complex in Jupiter, Fla., during spring training last year.

Federal agents were able to trace at least one of the breaches directly back to that computer. At least four members of the team's baseball operations staff have hired criminal defense lawyers, according to people briefed on the investigation.

"To put it simply, investigators are trying to match up the intrusions with the different times that different Cardinals front-office personnel were on the computer," said one person briefed on the case. "It has been very difficult."

Another person briefed on the investigation added, "The FBI has some sense of how long different guys were on the computer, but it hasn’t been easy."