NEW YORK (AP) — New York City on Wednesday marked the anniversary of the 1993 bombing at the old World Trade Center, when Islamic extremists first attempted to bring down the twin towers with 1,200 pounds of explosives in a parked rental van.

Six people, including a pregnant woman, died in the blast on Feb. 26 of that year.

Relatives of the victims gathered on the Trade Center’s memorial plaza to lay flowers and read the names of their lost loved ones.

A bell tolled at 12:18 p.m., marking the moment when the van exploded in the center’s underground parking garage.

“We gather to pay tribute to the innocent people killed and the more than 1,000 people who were injured that day,” said Beth Hillman, president and CEO of the 9/11 Memorial & Museum. “It is our steadfast mission and a great privilege to preserve the history of this tragic event, to honor those individuals who died, to stand in shared grief with you, their family and friends, and share with the world their stories, the courage of first responders and the resilience of those who survived.”

Earlier in the day, The Port Authority of New York and New Jersey, which owns the Trade Center site and lost four employees in the 1993 attack, paid tribute to them with a Mass at St. Peter’s Church nearby.

Six people, including accused ringleader Ramzi Yousef, were convicted in the bombing, which left a 150-foot-wide (45-meter-wide) crater inside the Trade Center’s parking garage.

The damage was repaired, but extremists struck again on Sept. 11, 2001, destroying the twin towers and killing nearly 3,000 people. Khalid Sheikh Mohammed, the self-proclaimed mastermind of 9/11, was Yousef’s uncle.

A fountain honoring those killed in the 1993 bombing was destroyed when the towers fell, but the dead are now honored on the same plaza where two large pools of falling water mark the spots where the skyscrapers once stood.