WASHINGTON - Immigration desk computers at various airports went down for about two hours on Monday, causing long lines for travelers entering the United States after year-end holidays, according to Customs and Border Protection and posts on social media.

The processing system outage began at about 7:30 p.m. EST (0030 GMT) and was resolved about 9:30 EST (0230 GMT), the customs agency said in a statement. All airports were back on line after wait times for travelers that were longer than usual, it said.

"At this time, there is no indication the service disruption was malicious in nature," the agency said. It gave no explanation for the disruption and said travelers were processed using alternative procedures.

All airports are back on line after a temporary outage of #CBP’s processing systems. During the disruption, CBP had access to national security-related databases and all travelers were screened according to security standards. No indication the disruption was malicious in nature.

— CBP (@CustomsBorder) January 2, 2018

Travelers entering the United States from overseas posted photos on social media of long lines at John F. Kennedy International Airport in New York and at Hartsfield-Jackson Atlanta International Airport.

"No one has been getting past JFK Airport immigration for the last hour. Line is a few 100 deep. Seems like their system did completely go down. Happy New Year!" said Jessica Yang, a program manager at Microsoft, in a Twitter post.

Other airports, including Denver International Airport, also said they were affected. A similar computer outage occurred a year ago.

"Operations returning to normal as @CustomsBorder computer issue resolved. Issue affected other US airports. Thanks for your patience," Miami International Airport said in a Twitter post.