The Latest: Community service mark bombing anniversary

BOSTON (AP) The Latest on Boston's efforts to mark the third anniversary of the Boston Marathon bombings (all times local):

3 p.m.

A moment of silence has been observed to mark the moment when the first of two bombs exploded at the Boston Marathon finish line three years ago.

Mayor Marty Walsh, bombing survivors and families of the victims bowed their heads in silence as church bells rang at 2:49 p.m. Friday, the minute the first bomb went off.

Three people were killed and more than 260 were injured on April 15, 2013.

One of the bombers, Dzhokhar Tsarnaev, was sentenced to death. His brother, Tamerlan, died in a gunfight with police in the days after the attack.

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2:40 p.m.

The U.S. Postal Service says it will seal dozens of blue mail collection boxes along the Boston Marathon route in the interest of safety and security.

The Postal Service made the announcement Friday amid the remembrances of the third anniversary of the marathon bombings.

The boxes will be sealed at the time of the last mail collection Saturday and reopened Tuesday. The marathon is Monday.

The closures affect boxes along the entire route from Hopkinton to Boston.

Security along the route has been bolstered since two pressure cooker bombs hidden inside backpacks were detonated near the finish line in 2013, killing three and injuring more than 260.

Among the items organizers have banned from the marathon are packages or other bulky items and certain containers.

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1:15 p.m.

The families of victims of the 2013 Boston Marathon bombings are doing community service projects in the city on the third anniversary of the attacks.

Members of 8-year-old victim Martin Richard helped clean a busy commercial street and square in their Dorchester neighborhood.

Family friend Sheila McCarthy says dozens of volunteers have been out since the morning hours picking up trash and planting flowers as a way to help and support the family, which picked the service project.

It was among a number of community service activities happening throughout the city, including blood drives, food and clothing collections, and other projects.

The family of Lingzi Lu, a 23-year-old Boston University graduate student killed in the attack, was expected to making a donation to the Police Department's Athletic League in City Hall.

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8:45 a.m.

Massachusetts Gov. Charlie Baker and Boston Mayor Marty Walsh joined dozens of others for a simple and somber wreath-laying ceremony to remember the victims of the 2013 Boston Marathon bombing.

Baker, joined by the father of victim Krystle Campbell, bowed his head in silence on Friday morning after laying a wreath at the site of one explosion. Walsh, with the family of victim Martin Richard, placed a wreath at the second blast site.

At 2:49 p.m., a citywide moment of silence will mark the time when the first of two pressure cooker bombs detonated near the race's end, killing three people and injuring over 260 others.

Throughout the day, residents will be taking part in blood drives, food and clothing collections and other community service projects to celebrate Boston's generosity and resilience.