A bomb has exploded in the northern port city of Zarautz, slightly injuring three people, officials said Sunday.

Road assistance service DYA got an anonymous call at 1:30 a.m. saying a bomb would go off outside a construction company in Zarautz, a seaside city 34 miles from the French border in the Basque Country, a regional Interior Ministry spokesman said.

Police were inspecting the area near the Amenebar company's offices to the east of the city when a bomb went off about 2:30 a.m. Sunday.

One person, a local resident, was cut slightly by broken glass and two police officers were treated for minor ear damage, the spokesman told The Associated Press on condition of anonymity in keeping with government rules.

All three were treated at the scene for their injuries and did not require hospitalization, the official said.

The explosion follows the May 21 arrest in Bordeaux, France, of three suspected ringleaders of the violent separatist Basque group ETA.