WASHINGTON, March 5 (Reuters) - The website used by the

hackers responsible for the breach at UnitedHealth Group ( UNH )

has been replaced by a notice claiming it was seized by

international law enforcement.

But at least one of the law enforcement agencies allegedly

responsible for taking the gang down says it had nothing to do

with the operation, raising the possibility that the hackers

faked their own takedown.

A message posted to the website of the Blackcat hacking gang

early on Tuesday said it had been seized "as part of a

coordinated law enforcement action" by U.S. authorities and

other law enforcement agencies. Among the logos of non-American

agencies involved was that of Europol and Britain's National

Crime Agency.

U.S. officials and Europol did not immediately return

messages seeking comment, but a National Crime Agency

spokesperson told Reuters that "I can confirm any recent

disruption to ALPHV infrastructure is not a result of NCA

activity."

ALPHV is an alternate name for Blackcat. Repeated messages

sent to the hackers over several days have not been returned.