The hacking collective LulzSec says it has hacked into the website and database of the Arizona Department of Public Safety (DPS) and released details of staff, emails and correspondence on public file-sharing sites.
A number of DPS officers told the Associated Press that they had been inundated with calls to their home and mobile phones from strangers on Thursday night, and that they were trying to change their numbers.
A DPS spokesman confirmed that the agency's computer system had been breached and was taking additional security safeguards that he wouldn't disclose.
The hackers said they had specifically targeted the department in that state because of its tough immigration law "and the racial profiling anti-immigrant police state that is Arizona". Arizona has introduced tough identification laws which have been criticised by President Obama and others. However, they have been frozen due to legal challenges.
But even as the details were being released, pressure was growing on the group from rival hackers unhappy about what they see as a lack of discretion in the choices of its targets. LulzSec has taken credit for hacking into Sony Pictures Europe, a number of games sites including Eve Online and Sega, defacing the PBS website and attacking the CIA website, the US Senate computer systems and the UK's Serious Organised Crime Agency.
The collective said on its website that it was releasing "hundreds of private intelligence bulletins, training manuals, personal email correspondence, names, phone numbers, addresses and passwords belonging to Arizona law enforcement."
The LulzSec group also said it planned to release "more classified documents and embarrassing personal details of military and law enforcement" every week but it was unclear whether other Arizona agencies have been targeted.
Meanwhile rival hackers, including one called The Jester – an ex-US military member – have been concentrating on tracking down the group's website and identifying its members. The Jester said on Twitter on Thursday that he had traced the Lulz Security website to an ISP in Malaysia, and provided a program for people to help track it down.
Other hackers are also trying to gather data about the group, which the Guardian understands was weakened earlier this month after some members worried about the outcome of attacking US government sites. In the UK one man, Ryan Cleary, has been arrested by the police and charged with offences under the Computer Misuse Act relating to attacks on a number of sites including Soca's.
The Maricopa County Sheriff's Office in Arizona was taking unspecified countermeasures to protect its computer system, officials there said on Thursday night.
Manuel Johnson, a spokesman for the FBI's Phoenix division, said the agency was aware of the situation but couldn't comment on whether the FBI was investigating it.
The Arizona Republic reported that experts worked Thursday evening to close external access to DPS' system.
