Joan Gual was taken to the ports authority's headquarters by Guardia Civil officers. | Alejandro Sepúlveda

Joan Gual Torrella, the president of the Balearic Ports Authority, was arrested at Palma's Son Sant Joan Airport on Thursday after returning from a business trip. Officers from the Guardia Civil's criminal police were waiting for him and Juan Carlos Plaza, the ports authority's director, who was also arrested.

It is understood that both men showed total surprise at having been placed under arrest for alleged corruption. They fully cooperated with the officers.

At the same time as these arrests were being made, the Guardia Civil detained three other ports authority senior managers - José Fernando Berenguer, Armando Parada and Miguel Puigserver. The five spent Thursday night in the cells at the Guardia Civil's Palma headquarters. They were taken to the ports authority's headquarters on Friday morning and were present while searches were made of their respective offices.

The Guardia Civil are investigating alleged irregularities with contracts at ports in the Balearics. The case has apparently been under investigation for over a year and is being headed by Laura Pellón of the anti-corruption prosecution service.

The five men have declined to make statements to officers, saying that the case has been investigated in secret and that they have no information regarding the charges.

The Balearic government spokesperson, Pilar Costa, said on Friday that the government is unaware of what is being investigated.

The Balearic Ports Authority, although it obviously works closely with regional administrations, does not come under the Balearic government; it is the regional branch of the State Ports.