"We have initiated an investigation into whether or not the server [used in selling the tickets] was compromised deliberately ... whether or not there was a deliberate intrusion [that] compromised the site," said Laura Eimiller, spokeswoman for the FBI in Los Angeles, California.

The server was operated by Irvine, California-based Paciolan, the vendor for selling the World Series tickets. Eimiller said agents have contacted Paciolan officials. While she could not say whether the investigation was triggered by a complaint by the Rockies, she did mention that the FBI had received "a number of calls" regarding the site crash.

The Rockies used an online-only system to sell tickets to three potential World Series games at Coors Field, beginning 10 a.m. last Monday. The sales were soon canceled after only a few hundred buyers managed to complete their purchases.

The team at first said the ticketing system had 8.5 million "hits," but later blamed the failure on an "external malicious attack" without releasing specific details. When sales resumed Tuesday, nearly 50,000 tickets sold after a few hours, despite the slow processing times.