Washington ? A hand grenade that landed within 100 feet of President Bush during his visit last week to a former Soviet republic was a threat to his life and the safety of the tens of thousands in the crowd, the FBI said Wednesday.

The grenade was live but did not explode.

The White House, which initially said Bush never was in danger, said the incident May 10 in the Georgia’s capital has led to a review of security at presidential events.

FBI agents are still investigating in Tbilisi, where tens of thousands of people heard Bush speak in strong support of Georgia’s efforts at democratic development.

It was unclear how much danger the president faced.

According to the FBI’s initial investigation, the grenade failed to explode only because of a malfunction. The activation device deployed too slowly to hit the blasting cap hard enough, agent Bryan Paarmann said.

The grenade was a knockoff of a Soviet-designed RGD-5, a fragmentation grenade with a lethal range of about 100 feet, according to a source familiar with the incident, who spoke on condition of anonymity.

“We consider this act to be a threat against the health and welfare of both the president of the United States and the president of Georgia as well as the multitude of Georgian people that had turned out at this event,” Paarmann said.

No one in the U.S. delegation — Bush, his staff, members of the press that accompanied him and others — saw a grenade being tossed. There was no sign that anything was amiss during the president’s half-hour appearance in Freedom Square.

Bush and his aides did not hear about the incident until they were flying home aboard Air Force One, officials said.

The Secret Service is also reviewing the incident, including reports that some in the crowd evaded metal detectors.

Georgia has a large cast of potential culprits, including former government elites angry at President Mikhail Saakashvili’s anti-corruption crackdown, supporters of two separatist regions aligned with Moscow, terrorists from the Pankisi Gorge and Russian saboteurs.

A reward of about $11,000 was offered for information about those responsible.