Remy de la Mauviniere, Assciated Press
Police and rescuers work at the scene of an explosion in Paris Thursday, in which one person was killed and another seriously injured, according to the Interior Ministry.

PARIS — A parcel bomb exploded at a lawyer's office in central Paris on Thursday, killing a secretary and seriously injuring an attorney, but a motive was not immediately clear, officials said.

Other tenants in the building include a foundation that does research on the Holocaust and a law firm that President Nicolas Sarkozy helped to found. That firm is several floors down from the one that was targeted.

Ten people were being treated for shock, prosecutor Jean-Claude Marin said. Interior Minister Michele Alliot-Marie, speaking from Brussels, condemned the attack as "cowardly and odious."

Mayor Bertrand Delanoe said the bombed lawyer's office was on the same floor — the fifth — as the Foundation for the Memory of the Shoah, created in 2000 with an endowment from recovered funds that were confiscated from French Jews during World War II. It supports research and education about the Holocaust and Jewish culture.

He and other officials stressed, however, that the motive for the attack was unclear.

"Someone came to the office and left a package. The secretary who opened it in fact opened a parcel bomb. The parcel bomb killed her," said Christian Charriere-Bournazel, the president of the Paris bar association.

"We do not know the reasons for this attack," said Charriere-Bournazel.

Damien Laude, a construction worker who was across the broad Boulevard Malesherbes at the time of the explosion, said he heard a muffled blast. Afterward, he saw a blond woman carried out of the building.

"She was completely covered with blood, she was unconscious," he said. Afterward, Laude said, a man with a head wound also emerged. Police and emergency vehicles quickly filled the street and cordoned off several neighboring buildings.

Police officials identified the injured attorney as Olivier Brane, a specialist in property law. He was taken to a hospital for treatment, police said.

Marin said the package was a small wooden box that had two explosive devices inside. A messenger delivered the package, he said. He did not say if there were two explosions or one.

He said the law office did civil and commercial work, and that it was not immediately clear whether the package was addressed to a specific person.

"We are trying to assemble the scattered pieces and to collect witness accounts to find out who it was addressed to," he said.

Officials said several other people had light injuries, but their numbers were unclear.

Sarkozy's law office was opened in 1987, according to the company's Web site. The practice changed its name from Arnaud Claude-Nicolas Sarkozy after Sarkozy's election in May, and is now called Arnaud Claude and Associates.