Thousands of travelers arrived at their destination only to find their checked bags were left behind at the Phoenix Sky Harbor International Airport on Thursday after a Transportation Security Administration computer system suffered a technical issue that took the airport’s bag screening system out of operation.

The issue caused more than 3,000 bags to miss their flights between 6:45 a.m. and 9 p.m. on Thursday when the system — used to check bags for explosives — was brought back online, KSAZ reports.

“TSA is experiencing significant, unprecedented technical issues with its computer server allowing the automated screening of checked bags for explosives,” the TSA said in a statement Wednesday afternoon, urging travelers to get to the airport early and avoid checked bags if possible.

A rep for Phoenix Sky Harbor says that when the system went down, TSA agents began using a back-up process that involves K-9s and hand checking bags.

In some cases, the airport rep says bags were driven to nearby airports — which are actually hours away in Los Angeles, Las Vegas, and San Diego — for screening and then flown on to their destination.

The back-up process, while effective, is timely and caused many of the bags to miss their intended planes. The Sky Harbor rep urges passengers to make sure their carry-on bags were packed with enough items for a “few days.”

While there were no significant flight delays tied to the issue, passengers were not thrilled to learn their possessions were still in Phoenix.

“They said they had to do the bags manually, that’s all they said,” one traveler tells CBS5 AZ.

“It’s very stressful because I hope everything is still there that I packed because they’re hand-checking it, number one, and number two, that it gets there on time,” another passengers said.

The TSA says the issue was corrected at around 9 p.m. Thursday.

Update: @TSA has announced baggage screening is operational again at Sky Harbor. Thank you PHX travelers for your patience. — PHX Sky Harbor (@PHXSkyHarbor) May 13, 2016

Thursday’s baggage issues comes as the TSA is already facing criticism over increasingly long security lines across the country.

Some airports have threatened to fire the Transportation Security Administration over long lines at screening checkpoints, and other airlines are calling the agency onto the carpet, while an industry group has urged passengers to Tweet the photos of the seemingly unending lines.

System back online after thousands of bags missed flights out of Sky Harbor [CBS5 AZ]

TSA bag-screening issue causes major delays at Sky Harbor [KSAZ]