(CNN) -- A former top Colombian official survived an assassination attempt Tuesday after a daylight bombing in the country's capital, authorities said.
Fernando Londono, a former interior and justice minister, was among at least 39 people injured in the Bogota blast. He was being treated at a hospital, President Juan Manuel Santos said.
"I want to condemn this in the strongest terms," he said, adding that the motive for the attack was unknown.
Londono's driver and his head of security were killed, Santos said.
A chaotic scene unfolded as the blast hit a commercial neighborhood in a city where such attacks have become rare.
All the windows on a bus were blown out, and blood was all over the area, witness German Diaz said.
People panicked, he said. Some cried. Video showed shattered glass and scattered car parts covering the street as rescuers arrived.
Security cameras at the Bogota intersection recorded a man crossing the street while cars were stopped at a red light, CNN affiliate Caracol TV reported. The man threw a package at the vehicle Londono was riding in, then sped away on a waiting motorcycle, the CNN affiliate said.
Colombian authorities were offering a 500 million peso ($280,000) reward for information leading to the capture of those responsible for the attack, Santos said.
Earlier Tuesday, police detected and deactivated a car bomb in central Bogota.
Santos told reporters Tuesday evening that there was no evidence linking the two incidents.
Mayor Gustavo Petro suggested the attack could have something to do with the U.S.-Colombia Free Trade Agreement, which went into effect on Tuesday.
"We think it is a plan aimed at trying to destabilize the city on the precise day when the free trade agreement begins," he told reporters.
He urged the city's residents to remain calm and report anything suspicious to authorities.
Londono served as minister of interior and justice from 2002 to 2004 during the administration of President Alvaro Uribe.
He was known for being outspoken against leftist rebel groups, including the Armed Revolutionary Forces of Colombia, or FARC. Londono travels with a sizable security detail because of numerous threats against him.
Even as Santos said authorities were still trying to determine who was behind the blast, one police official blamed the rebel group.
"Nobody else could have done it, and we have reasons to say what we are saying," Bogota Police Chief Luis Eduardo Martinez told reporters, according to Caracol.
Analysts offered a similar assessment.
"It has all the hallmarks of a FARC operation," said Cynthia Arnson, director of the Latin America program at the Woodrow Wilson International Center for Scholars in Washington.
The bombing comes as recent Colombian government operations and policies have caused significant setbacks for the rebel group, she said.
"This kind of attack in Bogota has become extremely rare, but nonetheless seems designed to drive home a political point, that the guerrillas retain this capacity for violence," Arnson said.
Several bomb blasts occur every year in Bogota, but assassination attempts are uncommon, said Ben West, senior tactical analyst for Stratfor. The last one occurred in 2007, when a letter bomb was sent to the deputy education minister, he said.
In the 1980s and 1990s, high-profile attacks targeting government officials were more common in Colombia, he said.
"I'd say for about the past 10 years, it's been much more quiet," West said. "One attack doesn't make a trend. It could just be an outlier, but it is significant that it was an assassination attempt, not just a random bombing. ... It is a more sophisticated attack."
Local media reports have speculated that the attack could be connected with the trade agreement, he said, and some have suggested local criminal gangs could be behind it.
But the FARC seems to have the strongest motive and capabilities to mount such an attack, West said. The rebels could be responding to a new government approach that expands the focus of military operations beyond the group's leaders, he said.
"They're going after all the FARC members. They're trying to be more disruptive rather than surgical. If they're successful in this, it's going to get a response from the FARC," West said. "An attack like this, in Bogota, in the capital of the country, where the government is, it could be a response to the new strategy the government is taking."
Journalist Fernando Ramos contributed to this report from Bogota. Mariano Castillo and Catherine E. Shoichet reported from Atlanta.