An explosion damaged the printing facilities of a Basque newspaper in northern Spain as people worked inside early Sunday but no one was injured, the Interior Ministry said.

An apparent bomb detonated at the presses of El Correo near the port city of Bilbao at about 3 a.m. Sunday, a regional ministry spokesman said.

A story on the Web site of El Correo blamed the explosion on the violent Basque separatist group ETA. There was no immediate confirmation that the group was responsible.

El Correo said around 50 people were preparing Sunday's paper when the explosion blasted a 430-square-foot hole in a concrete wall.

"No type of warning was given, and it is through sheer luck that a tragedy was averted," the paper said on its Web site.

El Correo said whoever planted the device had to have climbed over a high security fence, which was also damaged by the blast.

The printing works of El Correo are located in Zamudio, an industrial estate just east of Bilbao's international airport.

The explosion follows the May 21 arrest in Bordeaux, France, of three suspected ETA leaders.

ETA has killed more than 825 people since the late 1960s in a violent campaign for an independent Basque homeland in northern Spain and southwestern France.(AP)