MEXICO CITY (Reuters) - Mexicans held a minute of silence on Wednesday to mark the anniversary of devastating earthquakes that struck the country in September 2017, and the postal service honored three search-and-rescue dogs in a stamp.

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More than 450 people were killed and tens of thousands of homes were damaged when the quakes hit Mexico 12 days apart.

Mexicans stood silently in the street with their fists raised aloft just after 1:14 p.m. (1814 GMT), the precise moment the second, deadlier quake struck the capital city and surrounding states on Sept. 19 last year.

Quake rescue workers had used the gesture to request quiet as they listened for signs of life below the rubble of fallen buildings. Specially trained dogs searched through the wreckage for survivors, and became symbols of the rescue efforts.

The Mexican postal service said in a statement it issued a 15 peso commemorative stamp for navy rescue dogs Frida, Evil and Ecko, showing them decked out in search goggles. All three worked to find trapped victims of both September quakes.

The Mexican navy said in July that Frida, a yellow Labrador, was a veteran of eight years of rescue operations extending from Haiti to Ecuador, Guatemala and Mexico. In that time, she had found 12 people alive and 41 bodies, the navy said.

After the minute’s silence, authorities triggered quake alarms in Mexico City and office workers began filing out of buildings in a mock emergency evacuation. The timing brought back traumatic memories for many city residents, including children who were at school when the quake struck.

“My daughter came out crying last year, and I think she’s going to be worried again today,” said Adriana Guerrero, waiting for her child outside a school in the wealthy Polanco area of Mexico City as pupils and teachers evacuated classrooms.

The 7.1 magnitude quake hit central Mexico last year hours after a memorial evacuation drill. It killed 370 people, most of them in the capital. Tens of thousands of buildings were damaged, and dozens died as a school and offices collapsed.

It followed a separate, 8.2 magnitude quake off the southwest coast on Sept. 7 that killed about 100 people.

Hundreds of people in Mexico City have been unable to return to their homes since the quakes and some staged protests on Wednesday to complain about a lack of government support.

Even before the disaster last year, Sept. 19 had been ingrained in the minds of older residents of the capital, who remembered a massive 1985 earthquake that killed thousands of people in the city on that date.