A bomb exploded in front of the U.S. Consulate in the Costa Rican capital Thursday night, injuring three people, authorities said.
Police said three people, including a Panamanian, were detained in connection with the 9 p.m. blast. They were not identified.
The three injured, believed to be passers-by, were taken to San Juan Adios Hospital. Their conditions were not immediately known.
In Washington, State Department spokesman Joe Reap said, "We don't believe there were any American citizens injured, and I understand there's minor damage to the consular building."
The blast shattered windows and damaged doors of businesses in the area.
U.S. Ambassador Lewis A. Tambs, who appeared at the site of the explosion, called it a terrorist act.
But police speculated that the nearby office of the Panamanian Tourism Institute may have been the intended target.
Mark Krishchik, spokesman for the U.S. Embassy, said the explosion may have been caused by a hand grenade dropped across the street from the consulate.
He said damage to the consulate was minor and that there was no damage to the U.S. Embassy, which sits on the opposite corner of the intersection where the explosion occurred.
Investigators were searching for an individual who may have carried the device in a small suitcase. They said the explosive appeared to be homemade.