Former Pakistani Prime Minister Benazir Bhutto visited a Karachi hospital on Sunday to offer support to some of those wounded in a deadly suicide attack on her homecoming parade Thursday.
Flanked by heavy security, Ms. Bhutto waved to supporters after leaving Jenna Hospital.
Pakistani police are questioning three men about their possible involvement in the attack.
An investigator says the men are linked to a vehicle that police believe was used by someone who threw a grenade at Ms. Bhutto's motorcade. The grenade brought the convoy to a halt, and police say that seconds later, a suicide bomber blew himself up in the midst of a huge crowd cheering Ms. Bhutto's return to Karachi.
The blast killed nearly 140 people and wounded hundreds of others.
The police investigator says the three men were detained in the southern part of Punjab province, Pakistan's most populous area, and brought to Karachi for interrogation.
Police also have released a photograph of the suspected suicide bomber, who has not yet been identified.
In several neighborhoods of Karachi Saturday, people burned tires and threw rocks at passing cars to protest the attack, which turned Ms. Bhutto's joyful homecoming celebration into a scene of carnage and suffering.
Ms. Bhutto told reporters Friday that she had been tipped by a foreign government that four assassination teams were planning attacks as soon as she returned to Pakistan from eight years in self-imposed exile.
A top Taliban commander has denied any involvement in Thursday's carnage, and no other group has claimed responsibility for the attack, which has drawn strong condemnation worldwide. President Pervez Musharraf has promised a thorough investigation.