Police forces in England and Wales could not access national fingerprint records for up to a week because of a computer failure, it has emerged.
The system can compare millions of prints from all over the country
The National Automated Fingerprint Identification System (Nafis) broke down last week after a database crash.
Most constabularies were affected for two days but one unnamed force was unable to use the records for a week.
The Home Office said fingerprint checks had been delayed but the crash had not stopped police arresting criminals.
BBC correspondent Margaret Gilmore said the crash happened last Wednesday.
It was the server linking forces together and not Nafis itself that failed, she said.
A Home Office spokeswoman said all forces were now processing fingerprints as normal.
"This is the first service delivery problem of its kind that Nafis has encountered in its six year history.
"Our first priority has been to restore forces' access to the national database."
A full investigation to "learn lessons" and "identify procedural and technical changes" would be launched to stop the system crashing again, she said.
"Data held on the database has not been compromised in any way and forces have continued to collect fingerprint data," she added.
Shadow commons leader Oliver Heald accused the government of "incompetence" on Thursday, telling the Commons there had been a string of failures with systems that "don't work".
These include systems at the Child Support Agency and Passport Agency, National Insurance computers and last week's crash at the Department for
Work and Pensions (DWP).
"It's not by chance that it's known as the 'naff' system," Mr Heald said.
"Doesn't it just sum up the incompetence of this government, that here we are under Labour with all these systems, none of which work?"
The government last week said the computer failure at the DWP had been "blown out of proportion".
It admitted 80,000 staff were not able to process new pensions and benefits claims for several days, but said regular payments were unaffected.
Nafis is able to compare millions of prints from all over the country and find a match within minutes.
The powerful tool is allied to the Police National Computer's Phoenix application, which holds information on criminal records, last known addresses, car details, aliases and accomplices.
At the scene of a crime, officers take impressions of fingerprints, which are then photographed and scanned into a computer.
Forces' fingerprint experts can then search Nafis for a match.