Bomb disposal experts carried out a controlled explosion at Luton airport on Monday in the first security alert of its kind since the terror threat was raised to severe last month.

Police were called after a suspicious package was discovered in the security search area, prompting thousands of passengers to be evacuated and incoming flights diverted.

The five-hour security alert ended shortly after 5pm, when bomb-disposal experts carried out a controlled explosion on the device, understood to have been a household item such as curling irons.

Bedfordshire police said that although the item was "deemed suspicious", they were confident it did not pose a threat to the public . No arrests were made.

The evacuation is the first security alert at a major UK airport since the terror threat level was raised from "substantial" to "severe" on 29 August in response to Islamic State militants in Iraq and Syria.

Several evacuated passengers used Twitter to describe the "chaos". "Being told to remain where we are on speakers, while at the same time being told to evacuate," wrote Luke Miller.

Paul Green, who was due to fly to Edinburgh, said the mood was "pretty calm" once passengers were evacuated but complained that they had been given no information by airport staff. If it wasn't for Twitter we wouldn't know anything."

Green had passed through security when the evacuation was announced. He said he suspected something was not right as he was approaching the x-ray scanners.

He said: "I was going through security and the queue suddenly disappeared behind me – this was about 20 minutes before the alarm sounded. It took about 10 minutes to evacuate everyone.

"There was a woman running around telling the x-ray operators something and I asked them what was happening but they didn't know."

Bedfordshire police said: "London Luton Airport is in the process of reopening following a security alert that took place earlier this afternoon.

"Officers were called to the departure terminal at 1.36pm after airport security raised concerns about an item that was passed through a security check in keeping with the airport's policies and procedures.

"Members of the public were evacuated from the terminal area as a safety precaution while the Explosive Ordnance Disposal (EOD) team were called in to undertake the necessary checks required.

"A controlled explosion was conducted at 5.15pm and it was confirmed that the item destroyed, although deemed suspicious, did not present a wider danger.

"Bedfordshire police can confirm that no one has been arrested in relation to this incident."

An airport spokeswoman said: "We understand passengers will be frustrated by the delays they are experiencing. We are working closely with the police to ensure passengers are not inconvenienced unnecessarily but we must ensure that the safety and security of all our passengers and staff remains our top priority."