Twenty-two Buddhist monks are in Sri Lankan police custody after customs officials found 110kg of high-grade cannabis concealed in their luggage, the largest ever drug bust at Colombo’s main international airport.

The group, mostly junior monks in training from temples across Sri Lanka, were alleged to have “carried about five kilos of the narcotic concealed within false walls in their luggage”, according to a Sri Lanka customs spokesperson.

The monks had spent four days on holiday in Bangkok and had “kush”, a potent strain of cannabis, hidden in their luggage when returning to Bandaranaike airport on Saturday, the spokesperson said. Video footage posted on social media showed monks at the airport hiding their faces with their robes.

The men were handed over to police and were taken before a magistrate on Sunday.

It was the largest single detection of kush at the South Asian country’s main international airport, according to officials, with the haul valued at 1.1bn rupees (£2.5m).

The local Daily News reported that the monks’ trip had been sponsored, and their phones contained photos of the group enjoying the holiday in “lay clothing”.

A 23rd monk, believed to have organised the trip, was arrested in a suburb of Colombo, police told the BBC world service’s Sinhalese station. According to the police spokesperson, the monk, who was not on the trip, told the other monks “these parcels are a donation” and that a van would come to collect the packages, the BBC reported.

A 21-year-old British woman was arrested in May last year with 46kg of the drug at the same airport. Charlotte May Lee, 21, from Coulsdon, south London, has said the drugs were planted in her luggage without her knowledge. She was also travelling to Colombo from Bangkok.

Agence France-Presse contributed to this report